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Showing papers on "Proteolytic enzymes published in 1972"


Journal ArticleDOI
TL;DR: The soils investigated exhibited optimal protease activity near pH 8.0 and 60°C, and were consistent in their preferential hydrolysis of dipeptide derivatives containing amino acids with hydrophobic side chains, however, soils varied widely in their relative activities towards a given diPEptide derivative and towards benzoyl arginine amide, a cationic substrate used in the assay of ‘trypsin-like’ enzymes.
Abstract: Conditions are described for the rapid and precise assay of soil proteases, using proteins and dipeptide derivatives as substrates in the absence of added bacteriostatic agents. The rate of substrate hydrolysis was proportional to the soil concentration; the release of amino compounds per unit weight of soil was directly related to the incubation time. The soils investigated varied widely in their pH, texture, organic matter content, and total exchangeable cations, but nevertheless exhibited optimal protease activity near pH 8.0 and 60°C, and were consistent in their preferential hydrolysis of dipeptide derivatives containing amino acids with hydrophobic side chains. However, soils varied widely in their relative activities towards a given dipeptide derivative and towards benzoyl arginine amide (BAA), a cationic substrate used in the assay of ‘trypsin-like’ enzymes. Benzyloxycarbonyl (Z) phenylalanyl leucine was hydrolysed most rapidly by all soils investigated. Activities towards Z-phenylalanyl leucine far exceeded those towards protein substrates and were highly correlated with the clay contents of the soils but not well correlated with the organic matter contents.

945 citations


Journal ArticleDOI
TL;DR: The staphylococcal protease hydrolyzes all of the seventeen different glutamoyl bonds studied, although those involving hydrophobic aminoacid residues with bulky side chains are cleaved at a lower rate.
Abstract: An extracellular protease of Staphylococcus aureus, strain V8, previously shown to cleave specifically the peptide bonds on the carboxyl-terminal side of either aspartate or glutamate residues in phosphate buffer (pH 7.8) hydrolyzes only glutamoyl bonds in either ammonium bicarbonate (pH 7.8) or ammonium acetate (pH 4.0). Of all aspartoyl bonds tested, only the Asp-Gly linkage is cleaved at a detectable rate. The staphylococcal protease hydrolyzes all of the seventeen different glutamoyl bonds studied, although those involving hydrophobic aminoacid residues with bulky side chains are cleaved at a lower rate.

640 citations


Book
01 Jan 1972
TL;DR: The Protein Nature of Enzymes.
Abstract: The Protein Nature of Enzymes. Enzyme Purification. Active Sites and Factors Responsible for Enzyme Catalysis. Rates of Reactions. Effect of Substrate Concentration on Rates of Enzyme-Catalyzed Reactions. Effect of Enzyme Concentration on Rates of Enzyme-Catalyzed Reactions. Kinetic Consequences of Enzyme Inhibition. Enzyme Inhibitors. Effect of pH on Rates of Enzyme-Catalyzed Reactions. Effect of Temperature on Rates of Enzyme-Catalyzed Reactions. Enzyme Cofactors. Classification and Nomenclature of Enzymes. Introduction to the Hydrolases. The Glycoside Hydrolases. Pectic Enzymes. The Esterases. The Nucleases and Biotechnology. The Proteolytic Enzymes. Ordinary and Limited Proteolysis. Introduction to the Oxidoreductases. Lactate Dehydrogenase. Glucose Oxidase. Polyphenol Oxidase. Xanthine Oxidase. Catalase and Peroxidase. Lipoxygenase (Lipoxidase).

591 citations


Journal ArticleDOI
TL;DR: Chromosome preparations treated for short periods with the proteolytic enzyme trypsin show well defined banding patterns, comparable to those obtained by more elaborate techniques, and it is possible to map in detail the position of chromosome rearrangements.
Abstract: Chromosome preparations treated for short periods with the proteolytic enzyme trypsin show well defined banding patterns, comparable to those obtained by more elaborate techniques.—With such patterns it is possible to map in detail the position of chromosome rearrangements.—A rare balanced A1–E18 translocation in a phenotypically normal female and the unbalanced product in her abnormal child has been used to demonstrate this mapping method.

426 citations


Journal ArticleDOI
02 Aug 1972-Nature
TL;DR: It was found that although the neuraminidase protein was completely degraded during proteolysis, the isolated haemagglutinin protein could be recovered almost unchanged from the incubation mixture and its preliminary chemical and antigenic characterization was reported.
Abstract: THE envelope of influenza viruses contains two morphologically and chemically distinct glycoproteins, a haemagglu-tinin and a neuraminidase, which recent experiments have indicated1 may be removed from the virion by treatment with the protease, bromelain. In an investigation of the mechanism of this phenomenon it was found that although the neuraminidase protein was completely degraded during proteolysis, the isolated haemagglutinin protein could be recovered almost unchanged from the incubation mixture. We report the subsequent purification and crystallization of the haemagglutinin and its preliminary chemical and antigenic characterization. The X-31 strain of A2/Hong Kong/682 was used in most of the experiments to be described. Viruses were grown in embryonated eggs, purified as described by Skehel and Schild3 and digested with bromelain as described by Compans et al.1. The smooth-surfaced virus particles which resulted were removed from the incubation mixture by centrifuging for 60 min at 100,000g and purified by sucrose density gradient centrifugation (20–60% sucrose in phosphate buffered saline (PBS) (100,000g, 16 h). The morphology of these particles in comparison with intact virus is shown in Fig. 1. It is clear that all of the envelope spike proteins were removed during proteolytic digestion; in agreement with these observations the shaved particles were completely devoid of the haemagglutinating and neuraminidase activities of the virus envelope proteins. Polyacrylamide gel electrophoretic analyses of the polypeptide composition of the particles also indicated that they contained only four of the seven polypeptides of the virus4 in the same proportions as these were present in the intact virus particles (Fig. 2b and c). Both haemagglu-tination and neuraminidase activities were completely destroyed during protease treatment. Electrophoretic analyses of the proteins present in the protease incubation supernatant after removal of the subviral particles indicated, however (Fig. 2a), that the major components of this mixture were two polypeptides of similar mobility to the haemagglutinin polypeptides previously identified3. Thus, the mobility of the larger polypeptide of the supernatant was identical to that of the larger haemagglutinin component and the mobility of the smaller polypeptide indicated a molecular weight difference of approximately 3,000 between this and the smaller haemagglutinin polypeptide.

342 citations


Journal ArticleDOI
TL;DR: The senescence of oat leaves has been studied by following the loss of chlorophyll and protein and the increase of alpha-amino nitrogen, after detachment and darkening, and shown to be a sequential one in which protein synthesis, most probably the formation of a proteolytic enzyme with l-serine in its active center, is of prime importance.
Abstract: The senescence of oat leaves has been studied by following the loss of chlorophyll and protein and the increase of α-amino nitrogen, after detachment and darkening. Protein synthesis and the amounts of proteolytic enzymes in the leaves have been determined directly. The process of senescence is shown to be a sequential one in which protein synthesis,most probably the formation of a proteolytic enzyme with l-serine in its active center, is of prime importance. The evidence is as follows. Firstly, l-serine specifically enhances senescence, especially in presence of kinetin. Secondly, cycloheximide, which inhibits protein synthesis in other systems, delays senescence and prevents the serine enhancement. Although requiring higher concentrations, cycloheximide can be as effective as kinetin in inhibiting senescence. It is shown directly that cycloheximide prevents protein synthesis in oat leaves under the same conditions as when it prevents senescence. Thirdly, leaves have been shown to contain two proteinases, with pH optima at 3 and 7.5, whose activity increases during senescence, even though the total leaf protein is decreasing. The amounts of both these enzymes present after 3 days are clearly increased by serine, and are greatly decreased by cycloheximide or by kinetin. The role of kinetin in delaying senescence thus may rest on its ability to suppress protease formation.

274 citations


Journal ArticleDOI
TL;DR: It is concluded that polypeptides are probably one of the major components of thePSD and that the structural integrity of the PSD depends on polypePTides because disruption of the covalent or hydrophobic bonding of these polyPEptides leads to a progressive loss of PSD structure.
Abstract: A fraction enriched in synaptic complexes has been isolated from rat brain. The major structural elements of synaptic complexes after isolation are a sector of pre- and postsynaptic plasma membranes joined together by a synaptic cleft and a postsynaptic density (PSD) located on the inner surface of the postsynaptic membrane. On its outer surface, the postsynaptic membrane has a series of projections which extend about halfway into the cleft and which occur along the entire length of the PSD. Proteolytic enzymes at high concentrations remove the PSD and open the synaptic cleft; at low concentrations the PSD is selectively destroyed. By contrast, the structural integrity of the PSD is resistant to treatment with NaCl, EGTA, and low concentrations of urea. Pre- and postsynaptic membranes also remain joined by the synaptic cleft after NaCl, EGTA, or mild urea treatment. High concentrations of urea cause the partial dissociation of the PSD. We conclude that polypeptides are probably one of the major components of the PSD and that the structural integrity of the PSD depends on polypeptides because disruption of the covalent or hydrophobic bonding of these polypeptides leads to a progressive loss of PSD structure.

266 citations


Journal ArticleDOI
18 Oct 1972-Nature
TL;DR: The topographic distribution of membrane Con A sites becomes more clustered after treatment with proteolytic enzymes, and these sites appear to be involved in the formation of intercellular Con A cross-bridges between agglutinated cells.
Abstract: The topographic distribution of membrane Con A sites becomes more clustered after treatment with proteolytic enzymes. The clustered sites appear to be involved in the formation of intercellular Con A cross-bridges between agglutinated cells.

237 citations


Journal ArticleDOI
TL;DR: The main results are changes in pancreatic exocrine enzyme activities studied in different forms of experimental diabetes in rats and the effects of adrenalectomy on these changes were measured.
Abstract: . Changes in pancreatic exocrine enzyme activities were studied in different forms of experimental diabetes in rats. The effects of adrenalectomy on these changes were measured. The early actions of insulin on pancreatic enzyme activities and on incorporation of (4,5-3H)-leucine into amylase were also determined. The main results are: 1) Alloxan-diabetes leads to a decrease in amylase activity, a decreased rate of amylase synthesis and an increase in the activities of trypsinogen and chymotrypsinogen as described by Palla et al. [9]. Only the decrease in amylase activity correlates with the increase in blood glucose concentration. 2) Adrenalectomy does not reverse the changes in the activities of exocrine pancreatic enzymes induced by diabetes. 3) Diazoxide-diabetes is accompanied by an increase in all pancreatic enzyme activities, most probably due to the inhibition of enzyme secretion. 4) After treatment with streptozotozin a significant decrease in pancreatic amylase activity appears after 36 h. Amylase activity continues to fall during the following days, in contrast the increase in the activities of proteolytic enzymes is not significant until the 4th day. 5) Insulin treatment of severely diabetic, non-ketotic rats leads, as early as 90 min. after injection, to a significant increase in pancreatic amylase activity with no change in the other exocrine enzyme activities. A decrease in all enzyme activities, seen 6 h after insulin, is due to enhanced enzyme secretion. 6 As soon as 2 h after injection insulin leads to a significant increase in the incorporation of (4,5-3H)-leucine into pancreatic amylase but not into total pancreatic protein. This increase is completely abolished by actinomycin D. 7) Short-term effects of adrenalectomy (20 h) and effects of substitution with 6-α-fluoro-16α-methyl-prednisolon on the incorporation of (4,5-3H)-leucine into pancreatic amylase and total pancreatic protein result mainly from changes in the size of the cold leucine pool. According to these results insulin regulates pancreatic amylase synthesis mainly at the level of transcription. Insulin plays a permissive role in pancreatic amylase synthesis and is not involved in short-term regulation of amylase synthesis in the non-diabetic state. Clinical findings in juvenile diabetics indicate a similar type of regulation for amylase synthesis.

154 citations


Journal ArticleDOI
TL;DR: Renin in human amniotic fluid can be activated by the proteolytic enzymes pepsin and trypsin and activation of renin at pH 3.4.3–3.6 is due to an acid-stable factor which is inactive at physiological pH, and has properties similar to the enzyme pepin.

142 citations


Journal ArticleDOI
TL;DR: Functional studies, measuring strain under load, indicated that during 24-hour incubations of cartilage treated with trypsin or hyaluronidase these samples had much more evidence of strain than did collagenase-treated specimens, suggesting that collagen has the primary role in determining form of Cartilage and may be capable of significant water binding in the absence of proteinpolysaccharide.
Abstract: Cartilage has a great capacity to resist compressive force. This quality is related to its unique composition of proteinpolysaccharide in a mesh-work of collagen fibers. Although cartilage is not grossly altered in appearance in vitro by incubation with enzymes which can deplete proteinpolysaccharide, it becomes less stiff and more flexible. When slices of canine cartilage were incubated in 0.1M Tris-HCl, pH 7.6, 37°C, without prior freezing or addition of detergents, they spontaneously lost 60% of proteinpolysaccharide by the third day without concomitant loss of collagen. Specimens incubated with trypsin were depleted of 75% proteinpolysaccharide by the first 24 hours and, over a 1-week period, 20% of the collagen, although less than 2% was released during the last 2 days of incubation. Bacterial collagenase resulted in loss of approximately 9% of the total collagen during each day's incubation for 1 week, but the proteinpolysaccharide depletion followed a curve similar to controls. Functional studies, measuring strain under load, indicated that during 24-hour incubations of cartilage treated with trypsin or hyaluronidase these samples had much more evidence of strain than did collagenase-treated specimens. The latter lost actual thickness, however, while the trypsin-treated samples and controls remained the same size, suggesting that collagen has the primary role in determining form of cartilage and may be capable of significant water binding in the absence of proteinpolysaccharide. It is proposed that measurement of compressibility of articular cartilage is a suitable index of its effective proteinpolysaccharide content, and the total volume or thickness can be diminished only by agents capable of removing collagen.


Journal ArticleDOI
TL;DR: Coxsackie virus type A-9 seems to be an extreme example of this enteroviruses that was inactivated by proteolytic bacteria (notably Pseudomonas aeruginosa) in a limited survey.

Journal ArticleDOI
TL;DR: Of all the chemicals tested, turtle photoreceptor cells synthesized only acetylcholine, suggesting that these cells may be cholinergic.
Abstract: For determination of possible neurotransmitters synthesized by photoreceptor cells, turtle retinas were dissociated into single cells with proteolytic enzymes. These cells were partially separated by velocity sedimentation to yield a fraction rich in photoreceptors. Individual photoreceptor cells were then sucked into a micropipette and incubated with labeled precursors of known or suspected neurotransmitters. After incubation, the radioactive products were analyzed by high-voltage electrophoresis. Of all the chemicals tested, turtle photoreceptor cells synthesized only acetylcholine, suggesting that these cells may be cholinergic.

Journal ArticleDOI
TL;DR: There may exist at least two proteolytic systems in E. coli: one operating in all cells, which can degrade abnormal proteins, and one found in starving cells which is sensitive to sulfonyl fluorides and aromatic diamidines.

Journal ArticleDOI
TL;DR: Activities of 9 glycosidases were found to be significantly elevated in MSV-3T3 and RSV- 3T3 cells compared to 3T2 cells; acid phosphatase and β-glucuronidase levels were similar in the normal and RNA virus transformed cells.

Journal ArticleDOI
TL;DR: In this paper, a model system is presented which suggests both the origin and location of soil ureases and a reason for their persistence in nature, which suggests that some form of enzymeprotective mechanism exists in soil.
Abstract: Urease activity in soil is persistent for long periods under low water, low temperature, and sterile regimes, and it has been suggested that some form of enzyme-protective mechanism exists in soil.Dublin soil was sonicated in water and extracted by adding a mixture of salts. Urease activity is associated with the organomineral complex thus obtained and is resistant to the activities of proteolytic enzymes. Clay-free soil organic matter prepared subsequently by filtration also exhibits urease activity which is resistant to proteolysis. Models consisting of enzymes with bentonite and lignin were found to mimic this resistance to proteolysis. Models consisting of enzymes with bentonite and lignin were found to mimic this resistance to proteolysis.A model system is presented which suggests both the origin and location of soil ureases and a reason for their persistence in nature.

Journal ArticleDOI
TL;DR: The caldo-active strain YT-P was found to produce a variety of extracellular enzymes, including an amylase and a protease, which were further examined, and it is suggested that they belong to the genus Bacillus.
Abstract: The caldo-active strain YT-P was found to produce a variety of extracellular enzymes, including an amylase and a protease, which were further examined. With azo-casein as a substrate, optimum conditions with respect to enzyme and substrate concentration were determined for the protease. The optimum temperature was found to be 70°C, with a sharp decline to both lower and higher temperatures. The enzyme was found to be extremely heat-stabile, with unaltered activity after 8 hours at 80°C. Optimum conditions for the amylase were also examined. This enzyme was shown to be less heat-stabile, though the temperature optimum was again at 70°C. The activity or stability was not influenced by absence or presence of Ca-ions. The main activity of the amylase was found in the 20–40% ammonium sulfate fraction, which also contained the bulk of the proteolytic enzyme. This strain growth optimally on a variety of carbon sources at 72°C. Typical submicroscopical features are the double-layered cell wall, and a cytoplasmic membrane with a varying number of small dots and dot-free patches. Furthermore the nutritional requirements and submicroscopical features of two other strains, YT-G and YT-F, are described and compared to strain YT-P. Based on the fatty acid composition of the three spore forming caldo-active strains we suggest that they belong to the genus Bacillus, and propose the names B. caldolyticus for strain YT-P, B. caldovelox for strain YT-F, and B. caldotenax for strain YT-G.

Journal ArticleDOI
16 Aug 1972-Nature
TL;DR: Direct evidence that the control of cell growth is related to sialic acid residues on the cell surface is reported, which indicates that cell surface regulation may be important in regulating cell proliferation.
Abstract: THE proliferation of normal cells stops when the cultures have formed confluent monolayers; this process is termed density-dependent inhibition of growth (DDI). The cells can be released from DDI by proteolytic enzymes and other substances acting on the cell surface1, indicating that the cell surface may be important in regulating cell proliferation. Sialic acid residues also may be important in this regulation. Growing and virus-transformed cells contain less sialic acid in glycolipids2 and possibly also in glycoproteins3 than normal resting cells. We report direct evidence that the control of cell growth is related to sialic acid residues on the cell surface. Small concentrations of neuraminidase initiate proliferation in stationary cell cultures and cause an early increase in sugar uptake.

Journal ArticleDOI
TL;DR: In chick liver nuclei obtained after centrifugation, there is a receptor of high affinity for estradiol, binding estrogens but not non-estrogenic hormones, and sensitive to proteolytic enzymes and p -chloromercuribenzoate.

Journal ArticleDOI
A. Sivak1
TL;DR: Cell division, which can be induced by PMA or serum in stationary monolayers of BALB/c‐3T3 cells, is not blocked by several inhibitors of proteolytic enzymes or the plant lectins, concanavalin A or wheat germ agglutinin.
Abstract: Density dependent inhibition of cell replication is released in stationary cultures of BALB/c-3T3 fibroblasts by the potent tumor promoter for mouse skin, phorbol myristate acetate (PMA). The saturation density of these cultures, which is dependent on the serum concentration of the medium, is increased by PMA. Cell division, which can be induced by PMA or serum in stationary monolayers of BALB/c-3T3 cells, is not blocked by several inhibitors of proteolytic enzymes or the plant lectins, concanavalin A or wheat germ agglutinin. Induction of cell replication by PMA or serum does not appear to be dependent on proteolytic activity, and the membrane sites associated with this induction appear to be distinct from the agglutinin-binding sites.

Journal ArticleDOI
TL;DR: Evidence is presented that the second transition reflects hydrophobic lipid-protein interactions and the effect of protein conformational changes on the dynamic state of membrane lipids.

Journal ArticleDOI
TL;DR: Molecular weights of glycoproteins calculated from acrylamide gel electrophoresis were found to vary with the percentage of acrieslamide in the gel, indicating that these proteins do not behave in a normal fashion in this electrophoreis system.

Journal ArticleDOI
TL;DR: It is shown that the degranulation of mast cells, like the vasodilatation, is mediated by the somatic sensory axons supplying the skin.
Abstract: Immediately subjacent to a scratch damaging the epidermis of the external ear of the albino rat, all the dermal mast cells are degranulated. The proportion of degranulating mast cells is increased from about 43% to about 56% in areas of vasodilatation due to axon reflexes in the skin surrounding such a scratch. A similar degree of degranulation follows antidromic stimulation of the common trunk of the great auricular and lesser occipital nerves. It is shown that the degranulation of mast cells, like the vasodilatation, is mediated by the somatic sensory axons supplying the skin. A theory is advanced in which it is proposed that histamine, released from degranulated mast cells at the site of an injury, stimulates sensory nerve endings initiating an axon reflex. A transmitter substance, possibly adenosine triphosphate, is released from other terminations of the same neuron and causes degranulation of mast cells. Proteolytic enzymes released from these mast cells act upon a substrate present in the extracellular fluid to form bradykinin, which dilates nearby arterioles.

Journal ArticleDOI
TL;DR: The purified α-bungarotoxin-receptor complex was utilized to characterize and isolate an acetylcholine receptor from guinea pig cerebral cortex and had the properties of protein, indicating that the receptor is probably a protein3 cerebral cortex or higher, and showed optimum binding at pH 7.7.

Journal Article
TL;DR: In this article, the authors demonstrate morphologic correlates of exposure of skin to exfoliative toxin derived from live phage group II staphylococci, which is associated with scarlatiniform rash, generalized exfoliation, or bullous impetigo.
Abstract: The purpose of this study was to demonstrate morphologic correlates of exposure of skin to exfoliative toxin derived from live phage group II staphylococci. Human infection with these staphylococci has been associated with scarlatiniform rash, generalized exfoliation, or bullous impetigo. Histologically, the skin lesions in patients and animals injected with the exfoliative toxin appear indistinguishable. The characteristic change is an intraepidermal cleavage through the granular cell layer. Electron microscopically, this cleavage appears to result from disruption of otherwise normal attachment structures (desmosomes) through their intercellular contact area. This disruption may be related to disappearance of extracellular globules which are proposed possibly to contain proteolytic enzymes.

Journal ArticleDOI
TL;DR: Neurospora crassa strain 74A grown on Vogel's medium containing bovine serum albumin (BSA) as principal carbon source secretes proteolytic enzymes which appear in the culture filtrate, causing a five-fold increase in the amount of protease production.
Abstract: Neurospora crassa strain 74A grown on Vogel's medium containing bovine serum albumin (BSA) as principal carbon source secretes proteolytic enzymes which appear in the culture filtrate. Low concentrations of sucrose (0.1%) are necessary for growth from conidia, as conidia will not germinate on BSA alone. Once growth is initiated, however, protease production begins and at 5 to 6 hr growth and enzyme production are parallel. Higher concentrations of sucrose (0.5-2%) repress protease synthesis. Other metabolizable materials (sugars, amino acids, peptide mixtures) also repress protease synthesis. Some sugars will not sustain growth but allow germination and full induction of protease in the presence of protein. A material found in culture fluids of cells during induction of protease synthesis when added to repressed cultures causes a five-fold increase in the amount of protease production, although this is still approximately half that of normally induced cells. This material appears to be produced by induced cells in as little as 2 hr of culture, which is before detectable levels of protease can be found. It is heat-stable, of low molecular weight, and is not a simple product of protein digestion by the N. crassa proteases.

Journal Article
TL;DR: What is possibly an important mechanism by which leukocytes accumulate in chronic inflammatory areas is described, namely, that macrophage proteinase could, from C5, produce C5a which attracts more macrophages and PMN to the site.
Abstract: When the activation of complement proceeds through its fifth component (C5), a chemotactic fragment (C5a) is released (1–3) which attracts both macrophages and polymorphonuclear leukocytes (PMN). 4 Proteolytic enzymes such as trypsin and PMN neutral proteinase also release C5a from C5 (2–4). This report shows that an acid-acting proteinase from both macrophages and lung (a tissue rich in macrophages) (5–7) could do likewise. It therefore describes what is possibly an important mechanism by which leukocytes accumulate in chronic inflammatory areas, namely, that macrophage proteinase could, from C5, produce C5a which attracts more macrophages and PMN to the site. Two sources of macrophage proteinase were used in these experiments. The acid-acting proteinase was partially purified from beef lung by the method of Dannenberg and Smith (5, 6), and further purified on CM-Sephadex columns. Homogenates of either peritoneal or pulmonary macrophages from rabbits also served as a source of this proteinase (7).

Journal ArticleDOI
TL;DR: It is proposed that conformational changes in the γG antibodies or a specific molecular arrangement in the lattice work of complexes containing large protein antigens may influence the biological properties of the soluble complexes.
Abstract: The adherence of soluble immune complexes to stimulated alveolar macrophages was studied in vitro using HSA-anti-HSA complexes prepared in antigen excess. Those complexes containing more than two molecules of antibody preferentially adhered to macrophages in the absence of complement. Free gammaG in less than physiological concentrations inhibited the adherence of complexes, and the presence of complement did not significantly alter this inhibition. Complexes prepared with reduced and alkylated antibodies showed a decreased adherence. The strength of binding of soluble complexes to macrophages and their efficiency in fixing complement were greater than seen with small aggregates of homologous gammaG. These differences in biological properties were observed even though the immune complexes and aggregates contained comparable numbers of gammaG molecules. The gammaG receptor on rabbit macrophages exhibited species specificity. Pretreatment of macrophages with proteolytic enzymes led to adherence of larger amounts of soluble complexes. These observations suggest that the strength of binding of soluble immune complexes to macrophages and their efficiency in fixing complement are not determined solely by a random summation of individual binding sites. It is proposed that conformational changes in the gammaG antibodies or a specific molecular arrangement in the lattice work of complexes containing large protein antigens may influence the biological properties of the soluble complexes.

Journal ArticleDOI
TL;DR: The membrane polypeptides in their native state in intact cells were relatively resistant to low dose Pronase digestion in contrast to the high sensitivity of the isolated membrane fragments to enzyme digestion.