Showing papers on "Proteolytic enzymes published in 1996"

Strategies for Protein Purification and Characterization A Laboratory Course Manual

Abstract: Part 1 Purification of calmodulin. Experiments: activity assays - assay of calmodulin fractions preparation of a tissue extract bulk fractionation ion-exchange chromatography hydrophobic interaction chromatography characterization of calmodulin - calculation of recovery characterization of calmodulin - electrophoresis proteolytic digestion reverse-phase HPLC physical analysis of calmodulin chemical analysis of calmodulin. Preparation of reagents. Part 2 Purification of transcription factor AP-1 from HeLa cells. Experiments: preparation of a nuclear extract from HeLa cells gel filtration chromatography with Sephacryl S-300 HR sequence-specific DNA affinity chromatography DNase 1 footprinting gel-mobility-shift assay preparation of heparin-sepharose CL-2B preparation of reagents. Part 3 Purification of recombinant protein overproduced in escherichia coli. Experiments: breakage of E. coli cells and preparation of inclusion bodies solubilization, refolding, and ion-exchange chromatography of the inclusion body pellet (o32) polyethyleneimine precipitation and immunoaffinity chromatography of the soluble extract (core RNA polymerase o32 complex) quantitation and summary of preparation protein characterization. Protocol development trials - purification of o32 from a bacterial overexpresser preparation of reagents. Part 4 Solubilization and purification of the rat liver insulin receptor. Experiments: isolation of plasma membranes from rat liver solubilization of insulin receptor from membranes lectin affinity chromatography of solubilized receptors insulin affinity chromatography of partially purified receptors cross-linking of insulin receptors with [125I] insulin insulin-stimulated insulin receptor autophosphorylation analysis of insulin receptor glycosylation. Preparation of reagents.

Angiotensin Receptors and Their Antagonists

Abstract: Angiotensins are peptide hormones derived from the protein precursor angiotensinogen by the sequential actions of proteolytic enzymes (Figure 1). The classic pathway of angiotensin synthesis includes a reaction catalyzed by angiotensin-converting enzyme (ACE), which occurs not only in plasma but also in the kidneys, brain, adrenal glands, ovaries, and possibly other tissues.1 The intrarenal renin–angiotensin system affects glomerular filtration, as discussed below, but the importance of angiotensin synthesis in other tissues is not known. Angiotensin II, the principal effector of the renin–angiotensin cascade, can also be synthesized by a pathway that does not require ACE.2 Angiotensin II stimulates a variety . . .

Assembly of the phagocyte NADPH oxidase: molecular interaction of oxidase proteins.

Abstract: Phagocytes such as neutrophils play a key role in the body's innate immune response to infection. These cells travel throughout the body in search of pathogens and are rapidly mobilized to sites of inflammation where they phagocytose these pathogens and subsequently release a variety of toxic oxygen radical species and proteolytic enzymes to directly destroy the engulfed particle. The generation of microbicidal oxidants by neutrophils results from the action of a multi-protein enzymatic complex known as the NADPH oxidase. Altogether, there are currently seven proteins reported to be associated with the NADPH oxidase assembly. In resting neutrophils, these NADPH oxidase protein components are segregated into cytoplasmic and plasma membrane compartments. However, during assembly and activation of the NADPH oxidase, the cytosolic protein components translocate to the plasma membrane or phagosomal membrane where they assemble around a central membrane-bound protein known as flavocytochrome b. This assembly process is highly regulated and involves multiple binding interactions between the individual NADPH oxidase proteins, resulting in an active oxidase complex. Over the past few years, a number of these sites of binding interaction between the oxidase proteins have been identified, leading to a clearer understanding of the intermolecular interactions occurring among protein components during the assembly process. In addition, this information has contributed to our understanding of the roles played by each protein during the activation and assembly process. In this review, we describe the key features of each NADPH oxidase protein and then summarize our current understanding of the specific molecular interactions occurring between these proteins, focusing on the role these protein:protein binding interactions play in the NADPH oxidase assembly process.

Enhancing the functionality of food proteins by enzymatic modification

Abstract: Proteins are increasingly being utilized to perform functional roles in food formulations. Common food proteins possess good functional properties including solubility, gelation, emulsification and foaming. The functional properties of proteins are impaired near their pl (isoelectric point), as is the case in most acidic foods. Enzymatic modification of food proteins by controlled proteolysis can enhance their functional properties over a wide pH range, and other processing conditions. Choosing the right proteolytic enzyme, environmental conditions for hydrolysis and degree of hydrolysis is crucial for enhancing the functional properties of proteins. Understanding the molecular properties required for protein functionality and the development of strategies to achieve them are critical for developing and utilizing modified protein ingredients. Numerous reports on enhancing the functionality of food proteins by limited proteolysis have been published, some of which are reviewed in this article.

Phagocytosis and intracellular digestion of collagen, its role in turnover and remodelling

Abstract: Collagens of most connective tissues are subject to continuous remodelling and turnover, a phenomenon which occurs under both physiological and pathological conditions. Degradation of these proteins involves participation of a variety of proteolytic enzymes including members of the following proteinase classes: matrix metalloproteinases (e.g. collagenase, gelatinase and stromelysin), cysteine proteinases (e.g. cathepsin B and L) and serine proteinases (e.g. plasmin and plasminogen activator). Convincing evidence is available indicating a pivotal role for matrix metalloproteinases, in particular collagenase, in the degradation of collagen under conditions of rapid remodelling, e.g. inflammation and involution of the uterus. Under steady state conditions, such as during turnover of soft connective tissues, involvement of collagenase has yet to be demonstrated. Under these circumstances collagen degradation is likely to take place particularly within the lysosomal apparatus after phagocytosis of the fibrils. We propose that this process involves the following steps: (i) recognition of the fibril by membrane-bound receptors (integrins?), (ii) segregation of the fibril, (iii) partial digestion of the fibril and/or its surrounding non-collagenous proteins by matrix metalloproteinases (possibly gelatinase), and finally (iv) lysosomal digestion by cysteine proteinases, such as cathepsin B and/or L. Modulation of this pathway is carried out under the influence of growth factors and cytokines, including transforming growth factor beta and interleukin 1 alpha.

Matrix Metalloproteinases in the Normal Human Central Nervous System, Microglial Nodules, and Multiple Sclerosis Lesions

Abstract: Matrix metalloproteinases (MMPs) comprise a family of proteolytic enzymes that are involved in remodeling of the extracellular matrix (ECM) of many tissues. They have been implicated in degradation of vascular basement membranes thereby facilitating leukocyte migration into inflammatory sites. To determine the cellular localization and levels of MMPs in the normal human central nervous system (CNS), multiple sclerosis (MS) lesions, and other conditions, cryostat sections of CNS samples were immunostained with antisera to MMP-1, -2, -3 and -9. In control white matter the principal cells that express the MMPs were perivascular and parenchymal microglia. Cellular MMP expression was also found in sporadic microglial nodules in MS white matter. Most CNS microvessel endothelial cells expressed MMP-3 and -9 but not MMP-1 or -2. The majority of macrophages in active MS and necrotic lesions were MMP-l-, -2-, -3-, and -9-positive whereas chronic MS lesions had fewer MMP-positive macrophages. Small numbers of astrocytes were MMP-2-, -3- and -9-positive in acute and chronic MS lesions. These data suggest that microglia-derived MMPs may mediate turnover of the CNS ECM under normal conditions and in microglial nodules. In sites of CNS tissue injury there is complex and dynamic regulation of MMP expression by different cell populations. In MS lesions MMP-mediated proteolysis may contribute to breakdown of the blood-brain barrier and leukocyte migration into the CNS, in situ immune activation, demyelination, metabolism of bioactive peptides, and the formation of an ECM that does not promote remyelination or axonal repair.

Adult human chondrocytes cultured in alginate form a matrix similar to native human articular cartilage.

Abstract: The matrix formed by adult human chondrocytes in alginate beads is composed of two compartments: a thin rim of cell-associated matrix that corresponds to the pericellular and territorial matrix of articular cartilage and a more abundant further-removed matrix, the equivalent of the interterritorial matrix in the tissue. On day 30 of culture, the relative and absolute volumes occupied by the cells and each of the two matrix compartments in the beads were nearly identical to those in native articular cartilage. Furthermore, the concentration of aggrecan in the cell-associated matrix was similar to that in adult human articular cartilage and was approximately 40-fold higher than in the further removed matrix compartment. Fluorescence-activated cell sorting revealed that the cell-associated matrix was built on the cell membrane in part via interactions between hyaluronic acid and CD44-like receptors. Approximately 25% of the aggrecan molecules synthesized by the chondrocytes during a 4-h pulse in the presence of [35S]sulfate on day 9 of culture were retained in the cell-associated matrix where they turned over with a half-life (t1/2) = 29 days. Most [35S]aggrecan molecules reached the further removed matrix compartment where they turned over much more slowly (t1/2 > 100 days). These results add support to the contention that aggrecan molecules residing in the pericellular and territorial areas of the adult human articular cartilage matrix are more susceptible to degradation by proteolytic enzymes synthesized by the chondrocytes than those that inhabit the interterritorial areas further removed from the cells.

The Trefoil Peptide Family

Abstract: The unique three-loop structure of the trefoil motif, formed by intrachain disulfide bonds in a 1-5, 2-4, 3-6 configuration between six conserved cysteine residues, is the defining feature of a recently recognized family of peptides. Expression of trefoil peptides is closely related to that of mucin glycoproteins in diverse biological sources. Three distinct members of the family (pS2, intestinal trefoil factor, and spasmolytic polypeptide) are produced in the mammalian gastrointestinal tract by mucus-secreting cells and targeted primarily for luminal secretion. The compact structure of the trefoil motif may be responsible for marked resistance of trefoil peptides to proteolytic digestion, enabling them to function in the harsh environment of the gastrointestinal lumen. Trefoil peptides are ectopically expressed adjacent to areas of inflammation within the gastrointestinal tract and may play an important role in both maintaining the barrier function of mucosal surfaces and facilitating healing after injury.

Von Willebrand factor: molecular size and functional activity

Abstract: Von Willebrand factor (vWF) is the largest protein found in plasma. It circulates in blood as a series of multimers ranging in size from 500 to 20,000 kDa. The variable molecular weight of vWF is due to differences in the number of subunits comprising the protein. vWF mediates platelet adhesion to subendothelium of the damaged blood vessel. Only the largest multimers are hemostatically active. Each vWF subunit contains binding sites for collagen and for platelet glycoproteins GPIb and GPIIb/IIIa. Multiple interactions of repeating binding sites in vWF multimers with adhesive protein(s) of the subendothelium and with receptors on the platelet surface lead to "irreversible" binding of platelets to the exposed subendothelium. Functional properties of vWF are typical of multisubunit proteins encoded by autosomal loci. The phenotype of von Willebrand disease is determined by the properties of the dysfunctional subunits which become incorporated into heteropolymeric forms of vWF. Absence of large vWF multimers, seen in type 2A von Willebrand disease and in myeloproliferative disorders, is associated with bleeding tendency. On the other hand, in patients with vWF multimers of supranormal size, as they occur in thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), there is an increased risk of thrombosis. Proteolytic enzyme(s) are involved in physiologic regulation of the polymeric size of vWF. We have purified from human plasma a protease cleaving vWF at the same peptide bond that is also cleaved in vivo. vWF was quite resistant against the protease in a physiologic buffer but was degraded at low salt concentration or in the presence of 1 M urea. It appears that a conformational change in the vWF molecule exposes the specific protease-sensitive peptide bond and thus enhances degradation of vWF multimers. In some variants of type 2A vWF, the cleavage site in the vWF subunit is more susceptible to proteolytic degradation than in normal vWF, whereas in patients with TTP or HUS the protease activity may be suppressed. vWF-degrading protease plays an important role in pathogenesis of congenital or acquired disorders of hemostasis and thrombosis.

Cystatins in health and disease

Abstract: Proteolytic enzymes have many physiological functions in plants, bacteria, viruses, protozoa and mammals. They play a role in processes such as food digestion, complement activation or blood coagulation. The action of proteolytic enzymes is biologically controlled by proteinase inhibitors and increasing attention is being paid to the physiological significance of these natural inhibitors in pathological processes. The reason for this growing interest is that uncontrolled proteolysis can lead to irreversible damage e.g. in chronic inflammation or tumor metastasis. This review focusses on the possible role of the cystatins, natural and specific inhibitors of the cysteine proteinases, in pathological processes.

Striking differences between the kinetics of regulation of respiration by ADP in slow-twitch and fast-twitch muscles in vivo.

Abstract: The kinetics of in vivo regulation of mitochondrial respiration by ADP was studied in rat heart, slow-twitch skeletal muscle (soleus) and fast-twitch skeletal muscle (gastrocnemius, plantaris, quadriceps and tibialis anterior) by means of saponin-skinned fibres. Mitochondrial respiratory parameters were determined in the absence and presence of creatine (20 mM), and the effect of proteolytic enzymes (trypsin, chymotrypsin or elastase) on these parameters was investigated in detail. The results of these experiments confirm the observation of Veksler et al. [Veksler, V.I., Kuznetsov, A. V., Anflous, K., Mateo, P., van Deursen, J., Wieringa, B. & Ventura-Clapier, R. (1995) J. Biol. Chem. 270, 19921-19929], who studied muscle fibres from normal and transgenic mice, that the kinetics of respiration regulation in muscle cells is tissue specific. We found that in rat cardiac and soleus muscle fibres the apparent K(m) for respiration regulation was 300-400 microM and decreased to 50-80 microM in the presence of creatine. In contrast, in skinned fibres from gastrocnemius, plantaris, tibialis anterior and quadriceps muscles, this value was initially very low, 10-20 microM, i.e. the same as that is in isolated muscle mitochondria, and the effect of creatine was not observable under these experimental conditions. Treatment of the fibres with trypsin, chymotrypsin or elastase (0.125 micrograms/ml) for 15 min decreased the apparent K(m) for ADP in cardiac and soleus muscle fibres to 40-98 microM without significant alteration of Vmax or the intactness of outer mitochondrial membrane, as assessed by the cytochrome c test. In fibres from gastrocnemius, trypsin increased the apparent K(m) for ADP transiently. The effects of trypsin and chymotrypsin were studied in detail and found to be concentration dependent and time dependent. The effects were characterised by saturation phenomenon with respect to the proteolytic enzyme concentration, saturation being observed above 1 microM enzyme. These results are taken to show that in cardiac and slow-twitch skeletal muscle, the permeability of the outer mitochondrial membrane to adenine nucleotides is low and controlled by a cytoplasmic protein that is sensitive to trypsin and chymotrypsin. This protein may participate in feedback signal transduction by a mechanism of vectorial-ligand conduction. This protein factor is not expressed in fast-twitch skeletal muscle, in which cellular mechanism of regulation of respiration is probably very different from that of slow-twitch muscles.

Membrane-type matrix metalloproteinases (MT-MMPs) in tumor metastasis.

Abstract: Activated gelatinase A is reportedly associated with tumor spread. We identified novel matrix metalloproteinases that localize on the cell surface and mediate the activation of progelatinase A. Thus, these progelatinase A activators were named membrane-type matrix metalloproteinase-1 and -2 (MT-MMP-1 and -2, respectively). MT-MMP-1 is overexpressed in malignant tumor tissues, including lung and stomach carcinomas that contain activated gelatinase A. This suggests that MT-MMP-1 is associated with the activation of progelatinase A in these tumor tissues. The expression of MT-MMP-1 also induced binding of gelatinase A to the cell surface by functioning as a receptor. The cell surface localization of proteinases has advantages over pericellular proteolysis. MT-MMP-1 and its family may play a central role in the cell surface localization and activation of progelatinase A and via this mechanism, tumor cell use exogenous progelatinase A to mediate the proteolysis associated with invasion and metastasis.

Bacterial-induced release of inflammatory mediators by bronchial epithelial cells.

Abstract: This review focuses on bacterial induction and release of inflammatory cytokines and adhesion molecules by human bronchial epithelial cells, with special reference to Haemophilus influenzae, a pathogen commonly associated with chronic bronchitis. Studies investigating the mechanisms underlying bacterial colonization of the airways and bacterial-induced chronic airway inflammation have suggested that these are likely to involve localization of bacteria to the site(s) of infection in the respiratory tract and induction of a local airway inflammation resulting in the initiation of epithelial damage. We have hypothesized that the gross airway epithelial damage observed in chronic infective lung disease is an indirect consequence of proteolytic enzymes and toxic oxygen radicals generated by large numbers of neutrophils infiltrating the airways. Furthermore, the infiltration and activation of the neutrophils is a consequence of increased release of proinflammatory mediators from the host respiratory epithelium, induced by bacterial products, such as endotoxin. This hypothesis is based on studies which have demonstrated that the concentrations of circulating cytokines, such as interleukin (IL)-8 and tumour necrosis factor-alpha (TNF-alpha), which have profound effects on neutrophil activity, are increased in endotoxaemia and that airway epithelial cells are a rich source of these cytokines. Support for this hypothesis is provided by studies of cultured human bronchial epithelial cells incubated either in the absence or presence of purified endotoxin preparations from nontypable and type b H. influenzae strains which have demonstrated that these endotoxins lead to significantly increased expression and/or release of proinflammatory mediators, including IL-6, IL-8, TNF-alpha and intercellular adhesion molecule-1 (ICAM-1). Treatment of the cells with steroids can downregulate the expression and/or release of these inflammatory mediators. Additionally, these studies have demonstrated that culture medium collected from endotoxin-treated cultures, 24 h after treatment, significantly increases neutrophil chemotaxis and adhesion to human endothelial cells in vitro.

Alkaliphiles — from an industrial point of view

Abstract: Organisms with pH optima for growth in excess of pH 9 are defined as alkaliphiles (or sometimes alkalophiles). Alkaliphiles contain prokaryotes, eukaryotes, and archaea. It is clear that many different taxa are represented among the alkaliphiles, and some of them are proposed as new taxa. Alkaliphiles can b isolated from normal environments such as garden soil, although counts of the alkaliphiles are higher in alkaline environments. Alkaliphiles have made a great impact in industrial applications. Biological detergents contain alkaline enzymes, such as alkaline cellulases and/or alkaline proteases that have been produced from alkaliphiles. The current proportion of total world enzyme production destined for the laundry detergents market exceeds 30%. Another important application is the industrial production of cyclodextrin with alkaline cyclomaltodextrin glucanotransferase. This enzyme reduced the production cost and paved the way for its use in large quantities in foodstuffs, chemicals and pharmaceuticals. Besides these applications, there are other possible applications in food and waste treatment industries.

In vivo resistance to a human immunodeficiency virus type 1 proteinase inhibitor : Mutations, kinetics, and frequencies

Abstract: Resistance to saquinavir (Ro 31-8959), an inhibitor of human immunodeficiency virus type I proteinase, was studied in peripheral blood mononuclear cell-derived proviral DNA from patients undergoing prolonged treatment. A Leu90-->Met exchange was the predominant resistance mutation in vivo; Gly48-->Val or doubly mutant virus was rarely observed. After 8-12 months of treatment with saquinavir alone (600 mg, 3 times/day) or in combination with zidovudine (200 mg, 3 times/day), approximately 45% of all patients carried provirus with mutant proteinase; the incidence was lower (22%) in patients treated with a combination of saquinavir, zidovudine, and dideoxycytidine. There was a good relationship between genotypic analysis of saquinavir resistance and data from virus assays, confirming that Leu90-->Met and Gly48-->Val are the essential exchanges in the proteinase that determine loss of sensitivity to this inhibitor. Absence of genotypic resistance correlated with a sustained decrease in plasma viral RNA. There was a positive correlation between a Met90 mutation and some residues at natural polymorphic sites (positions 10, 36, 63, and 71).

Characterization of the chemical and antimicrobial properties of piscicolin 126, a bacteriocin produced by Carnobacterium piscicola JG126.

Abstract: A novel peptide bacteriocin produced by the lactic acid bacterium Carnobacterium piscicola JG126 isolated from spoiled ham was purified and characterized. This bacteriocin, designated piscicolin 126, inhibited the growth of several gram-positive bacteria, especially the food-borne pathogen Listeria monocytogenes, but had no effect on the growth of a number of yeasts and gram-negative bacteria. Bactericidal activity was not destroyed by exposure to elevated temperatures at low pH values; however, bactericidal activity was lost at high pH values, especially when high pH values were combined with an elevated temperature. Piscicolin 126 activity was not affected by catalase, lipase, or lysozyme but was destroyed by exposure to a range of proteolytic enzymes. Piscicolin 126 was purified to homogeneity and was found to be a peptide having a molecular weight of 4,416.6 +/- 1.9. A sequence analysis revealed that this compound is a cystibiotic (class IIa) bacteriocin containing 44 amino acid residues and one intrapeptide disulfide ring. Piscicolin 126 has regions of homology with some other bacteriocins obtained from lactic acid bacteria and is most closely related to sakacin P and pediocin PA-1 (levels of identity, 75 and 55%, respectively). Addition of piscicolin 126 to a devilled ham paste test food system inhibited the growth of L. monocytogenes for at least 14 days. Piscicolin 126 was more effective than two commercially available bacteriocin preparations tested in the same system.

A proteolytic fragment of insulin-like growth factor (IGF) binding protein-3 that fails to bind IGFs inhibits the mitogenic effects of IGF-I and insulin

Abstract: Limited proteolysis of insulin-like growth factor binding protein-3 (IGFBP-3) is increasingly becoming recognized as an essential mechanism in the regulation of insulin-like growth factor (IGF) bioavailability, both in the bloodstream and at cellular level. Plasmin generated on contact with various cell types provokes proteolytic cleavages that are similar to those induced in vivo by (as yet unidentified) IGFBP-3 proteases. Experimental conditions were determined to achieve plasmin-induced limited proteolysis of recombinant human nonglycosylated IGFBP-3. Two major fragments of 22/25 kilodaltons (kDa) and one of 16 kDa were identified by Western immunoblotting and isolated by reverse-phase chromatography. The 22/25-kDa fragments correspond to the major approximately 30-kDa glycosylated fragment of IGFBP-3 in serum and the 16-kDa fragment, to one of the same size, that is nonglycosylated. Western ligand blot analysis, affinity cross-linking, and competitive binding experiments using radiolabeled IGF and unl...

92 kDa type IV collagenase (MMP-9) is expressed in neutrophils and macrophages but not in malignant epithelial cells in human colon cancer.

Abstract: Degradation of the extracellular matrix during cancer invasion is accomplished by the concerted action of several proteolytic enzymes, including matrix metalloproteinases (MMPs). We have studied the immunohistochemical localization of one of these enzymes, 92-kDa type IV collagenase (MMP-9), in short-term fixed specimens of 19 colon adenocarcinomas and 2 biopsies of adjacent normal colon. Staining was confined to neutrophils and macrophages, as identified by double staining. All neutrophils were positive in all cases. Some positively stained tumor-infiltrating macrophages were seen in 6 (32%) of the tumors, located adjacent to invasive tumor glands. No cancer cells were stained in any of the cases. In normal colon tissue, staining was only seen of scattered neutrophils in vessels and of macrophages in Peyer's patches. Routinely processed specimens from 7 of the 19 carcinomas were analyzed by in situ hybridization. In agreement with previous results, a MMP-9 mRNA signal was in all cases seen in a subpopulation of tissue macrophages surrounding invasive tumor glands, while no MMP-9 mRNA was detected in any other cell types, including neutrophils and cancer cells. Our results indicate that in this type of cancer all neutrophils contain MMP-9, which has been produced before they infiltrate the tumors; that a subpopulation of the tumor-infiltrating macrophages most likely in all cases produces MMP-9 but that the content of this protein is low due to a rapid turnover and that malignant epithelial cells do not produce or contain detectable amounts of MMP-9. These findings extend previous results indicating that stromal cells are actively involved in the generation and regulation of extracellular proteolysis during cancer invasion. © 1996 Wiley-Liss, Inc.

Identification and characterization of HsIV HsIU (ClpQ ClpY) proteins involved in overall proteolysis of misfolded proteins in Escherichia coli.

Abstract: Heat shock response in Escherichia coli is autoregulated. Consistent with this, mutations in certain heat shock genes, such as dnaK, dnaJ, grpE or htrC lead to a higher constitutive heat shock gene expression at low temperatures. A similar situation occurs upon accumulation of newly synthesized peptides released prematurely from the ribosomes by puromycin. We looked for gene(s) which, when present in multicopy, prevent the constitutive heat shock response associated with htrC mutant bacteria or caused by the presence of puromycin. One such locus was identified and shown to carry the recently sequenced hslV hslU (clpQ clpY) operon. HslV/ClpQ shares a very high degree of homology with members of the beta-type subunit, constituting the catalytic core of the 20S proteasome. HslU/ClpY is 50% identical to the ClpX protein of E. coli, which is known to present large polypeptides to its partner, the ATP-independent proteolytic enzyme ClpP. We show that, in vivo, HslV and HslU interact and participate in the degradation of abnormal puromycylpolypeptides. Biochemical evidence suggests that HslV/ClpQ is an efficient peptidase whose activity is enhanced by HslU/CIpY in the presence of ATP.

Collagenase: a key enzyme in collagen turnover.

Abstract: The primary agents responsible for cartilage and bone destruction in joint diseases are active proteinases that degrade collagen and proteoglycan. All four main classes of proteolytic enzymes are involved in either the normal turnover of connective tissue or its pathological destruction. These proteinases are made by different cells found within the joints. Both extracellular and intracellular pathways exist and individual enzymes can be inhibited by specific proteinaceous inhibitors that block their activity. Recent research has implicated the matrix metalloproteinases (MMPs) in many of the processes involved in joint diseases. The metalloproteinases are capable of degrading all components of the extracellular matrix. This family of proteinases contains a group of at least three collagenases that are capable of degrading native fibrillar collagen. Collagen degradation within joint disease is recognized as the irreversible step in the destruction of cartilage that leads to a failure in joint function. The collagenases are the enzymes necessary to initiate collagen turnover in normal connective tissue turnover and in disease.

Two wound-inducible soybean cysteine proteinase inhibitors have greater insect digestive proteinase inhibitory activities than a constitutive homolog.

Abstract: Diverse functions for three soybean (Glycine max L. Merr.) cysteine proteinase inhibitors (CysPIs) are inferred from unique characteristics of differential regulation of gene expression and inhibitory activities against specific Cys proteinases. Based on northern blot analyses, we found that the expression in leaves of one soybean CysPI gene (L1) was constitutive and the other two (N2 and R1) were induced by wounding or methyl jasmonate treatment. Induction of N2 and R1 transcript levels in leaves occurred coincidentally with increased papain inhibitory activity. Analyses of kinetic data from bacterial recombinant CysPI proteins indicated that soybean CysPIs are noncompetitive inhibitors of papain. The inhibition constants against papain of the CysPIs encoded by the wound and methyl jasmonate-inducible genes (57 and 21 nM for N2 and R1, respectively) were 500 to 1000 times lower than the inhibition constant of L1 (19,000 nM). N2 and R1 had substantially greater inhibitory activities than L1 against gut cysteine proteinases of the third-instar larvae of western corn rootworm and Colorado potato beetle. Cysteine proteinases were the predominant digestive proteolytic enzymes in the guts of these insects at this developmental stage. N2 and R1 were more inhibitory than the epoxide trans-epoxysuccinyl-L-leucylamide-(4-guanidino)butane (E-64) against western corn rootworm gut proteinases (50% inhibition concentration = 50, 200, and 7000 nM for N2, R1, and E-64, respectively). However, N2 and R1 were less effective than E-64 against the gut proteinases of Colorado potato beetle. These results indicate that the wound-inducible soybean CysPIs, N2 and R1, function in host plant defense against insect predation, and that substantial variation in CysPI activity against insect digestive proteinases exists among plant CysPI proteins.

Analysis of Protein Carbonyls with 2, 4-Dinitrophenyl Hydrazine and Its Antibodies by Immunoblot in Two-Dimensional Gel Electrophoresis

Abstract: Protein carbonyls are reported to increase in aging and in pathologies such as Alzheimer's disease and ischemic injury. Detailed study of this important issue has, however, been hampered by lack of an appropriate method to identify individual carbonylated proteins. We describe here an immunoblot method to identify individual carbonylated proteins. We describe here an immunoblot method to investigate protein carbonyls reactive to 2,4-dinitrophenyl hydrazine. Rabbit polyclonal antibodies against 2,4-dinitrophenyl hydrazine were used to study the proteins derivatized by the reagent in one- or two-dimensional polyacrylamide gel electrophoresis followed by immunoblotting. More than 25 proteins with high carbonyl contents were clearly demonstrated in two-dimensional immunoblot of rat tissue soluble proteins. The method could detect concentrations as low as 1 pmol of carbonyls. The signals were mostly abolished by prior treatment of tissue proteins with sodium borohydride to reduce carbonyls. Fragments generated by V8 protease digestion of a single protein exhibited signal intensities of varying degrees, indicating that carbonylation is not uniform in different amino acid sequences. Proteins treated with glucose or aldehydes gave rise to positive signals, suggesting that the finding of carbonyls in tissue proteins is not necessarily an indication of direct oxidation of side chains of amino acid residues.

Dietary proteinase inhibitors alter complement of midgut proteases

Abstract: Plant serine proteinase inhibitors (Pls) have the potential to restrict the growth and/or development of herbivorous insects. However, there are limitations to the efficacy of these Pls. An insect's susceptibility to a Pl is determined, at least in part, by the relative proportion of proteolytic enzyme activity in the midgut that is suppressed by that inhibitor. Insects adapt to dietary trypsin inhibitor in their host plant by secreting “inhibitor-resistant” trypsin(s). These “inhibitor-resistant” enzyme(s) may be the standard proteinase(s) secreted into the midgut (e.g., Pieris rapae), or may be enhanced following ingestion of proteinase inhibitor (e.g., Helicoverpa zea). In addition, insects may be pre-adapted to specific Pl(s), following adaptation to a Pl from the same family. For example, Pieris rapae is a crucifer specialist that is resistant to cabbage Pl, but is also resistant to Kunitz soybean trypsin inhibitor, a Pl in the same family as cabbage Pl, but from a non-host plant. The ultimate value of this pre-adaptation to herbivory by a species of insect will be determined by the number of different families of Pl in host plant(s) to which the species has adapted, and the distribution of those families among other species of plants. Thus, it is possible that the presence of a plant Pl limits herbivory by insect(s). However, multiple inhibitors, matched to the complement of enzymes in the insect's midgut, may be required to enhance this resistance of plants to herbivorous insects. © 1996 Wiley-Liss, Inc.

Erg, an Ets-family member, differentially regulates human collagenase1 (MMP1) and stromelysin1 (MMP3) gene expression by physically interacting with the Fos/Jun complex.

Abstract: Collagenase1 (MMP1) and stromelysin1 (MMP3) are extracellular proteolytic enzymes that degrade connective tissue macromolecules and basement membranes. Both genes are regulated by the Ets and Fos/Jun families of transcription factors/oncoproteins. Here, we show that two members of the Ets-family, Ets2 and Erg and their combinations differentially regulate collagenase1 and stromelysin1 promoter activity. In transiently transfected cells, Ets2 activates both promoters whereas Erg induces collagenase1 but not stromelysin1 promoter activity. Moreover, Erg completely inhibits stromelysin1 promoter activation by Ets2. In gel shift assays however, the Erg protein bound little or not to the collagenase1 promoter, whereas it bound to the stromelysin1 promoter. By site-specific mutagenesis, we identified one major site at -88 that abolished collagenase1 promoter activation by Erg. Surprisingly, mutation of the collagenase1 AP1 site at -73 also abolished the activation by Erg suggesting that Erg cooperates with Fos/Jun in collagenase1 promoter regulation. Indeed, gel shift and in vitro protein interaction studies showed that Erg binds to the Fos/Jun complex. Thus, Erg represents the first example of a transcription factor that can distinguish between the collagenase1 and stromelysin1 promoters in that when Erg is recruited by Fos/Jun at the promoter, it transcriptionally activates collagenase1 gene but not stromelysin1 expression.