Showing papers in "Molecular and Cellular Biochemistry in 1977"

Structure and molecular organization of the photosynthetic accessory pigments of cyanobacteria and red algae

Abstract: Cyanobacteria (blue-green algae) and Rhodophyta (red algae) contain high concentrations of photosynthetic accessory pigments (phycobiliproteins) which trap light energy in the region between 400 and 650 nm. The electronic excitation energy is then transferred along a chain of these pigments to the reaction center chlorophyll of Photosystem II by a radiationless induced resonance process.

Dose any enzyme follow the Michaelis-Menten equation?

Abstract: A literature search has been conducted to see to what extent steady-state kinetics studies in the period 1965–1976 have revealed deviations from Michaelis—Menten kinetics. It was found that over 800 enzymes have been reported as giving complex curves for a variety of reasons and a group by group classification of all these enzymes has been carried out listing all the types of variations reported and the authors' explanations. In addition, for highly complex curves, we have determined the minimum degree of the rate equation. There were very few determined attempts to demonstrate adherence to the Michaelis—Menten equation over a wide variety of experimental conditions and substrate concentration and almost invariably detailed experimental work revealed unsuspected complexities. For these reasons, it is concluded that the assumption that most enzymes follow the Michaelis—Menten equation can not be supported by an appeal to the literature.

Covalent phosphorylation in the regulation of glycogen synthase activity

Abstract: The enzymes of glycogen metabolism have contributed significantly to our understanding of the molecular basis of enzyme regulation. There are, consequently, a number of reviews of this area, and in particular glycogen synthase (UDPglucose 4-a-glucosyltransferase, EC 2.4.1.11) has been quite recently the subject of some rather comprehensive treatments 1'2 which it does not seem profitable to reiterate. Therefore, this article will concentrate on recent developments in the study of glycogen synthase. Since some of the newer findings, and notably the current interest in the multiply phosphorylated subunit, are somewhat provocative with regard to the functioning of synthase in the cell, it is timely to discuss the possible biological implications of multiple phosphorylation. Current considerations of the regulation of glycogen synthase derive from the original observations that the enzyme in muscle could exist in different kinetic forms, distinguishable by their susceptibility to glucose-6-P activation. The first evidence for the interconversion between these two forms came from experiments in which muscle was treated with insulin 3. Shortly afterwards, the changes in kinetic properties were correlated with the phosphorylationdephosphorylation of the enzyme 4. The concept evolved, then, of two distinct species of glycogen synthase. One form, which contained covalent phosphate, would have a very low ** an invited article. activity in the absence of glucose-6-P and was termed the D (dependent) enzyme. The other, lacking covalent phosphate and active even in the absence of glucose-6-P, was termed I (independent) enzyme. Table 1 shows a general anticipatory summary of some important properties of glycogen synthase and indicates some of the differences related with phosphorylation of the enzyme. Together with the proposal that the D form of synthase was inactive in viz)o 6, the nature of several hormonal influences on the interconversion of synthase species led to a functional significance for the phosphorylationdephosphorylation of the enzyme. Hormones mobilizing carbohydrate reserves, such as glucagon 7 and epinephrine s, would switch off glycogen synthesis by promoting the abundance of the inactive D form of synthase in liver and muscle. A hormone such as insulin, stimulating glycogen deposition, would turn on synthase by increasing the proportion of the active I form 3. The fundamental validity of this model of hormonal regulation has been verified in many laboratories. Further, the glycogen synthases from a number of sources have been shown to exist in forms differing as to glucose-6-P activation (for listings, see references 1 and 2). This is true even for some organisms lacking classical endocrine control, the enzyme from yeast being the best-studied example. A brief note concerning nomenclature is necessary. Where no confusion arises, we have

Fructose-1,6-bisphosphate, a regulator of metabolism

Abstract: Fructose-1, 6-bisphosphate affects the rate of a large variety of enzyme reactions. In some instances its role as a physiologic effector is well documented. In many cases the effects of fructose bishosphate on particular enzymes have been demonstrated in vitro but the link to physiologic conditions has not yet been established. It is the purpose of this paper to summarize the scattered findings in fructose bisphosphate as an effector of enzyme reactions and to draw some conclusions about the role of the compound in metabolic regulation.

The chemical heterogeneity of the fetal hemoglobin in normal newborn infants and in adults.

Abstract: About ten years ago during a study of the amino acid sequence of catalase at Caltech, attempts to cleave at methionyl residues with cyanogen bromide were unsuccessful. Consequently, one of us (J. Roger SHELTON) suggested that human fetal hemoglobin (Hb F) whose sequence had been determined at this institution 1': be used as a test protein. When this was done, six anticipated peptides could be isolated. As they were further examined as to identity, a tridecapeptide from the C-terminus of the 31 chain (now called 3'CB-3) had integral residues of all expected amino acids except gly~ine and alanine, Instead of 1.0 and 2.0 respectively, they were 0.7 and 2.3 as Mr. SHELTON found on analysis. The deviation from integral numbers was too great to be due to analytical error and other explanations were sought. Ultimately, it was determined that there exist two types of 3' chain in which position 136 may be occupied by either a glycyl or an alanyl residue 3. Subsequent studies of normal and variant fetal hemoglobins showed that the synthesis of these two 3' chains, termed

The polymerization reaction of muscle actin.

Abstract: Recent advances in the studies of the aggregation of G-actin monomers, containing one molecule of ATP, to long filaments of F-actin, with a concomitant hydrolysis of the nucleotide to ADP, are reviewed. With the aid of e-ATP, the association and dissociation rate constant of the nucleotide could be determined. The binding of the nucleotide is enhanced by the binding of one Ca++ ion, probably at a different site. The ΔG value of the Mg++ or Ca++ induced polymerization has been determined to −39 to −59 kJ/mole, the critical protein concentration for the ATP-G-actin to ADP-F-actin conversion is very strongly influenced by the concentration of bivalent cations. The rate constants of the protein monomers, and the rate and equilibrium constants for the propagation step show the process to be extremely cooperative. Actin shows the interesting phenomenon of translocational head-to-tail polymerization, which may be regulated by ATP.

Models for the active transport of cations...the steady-state analysis.

Abstract: We summarise the progress that has been made in the analysis of active transport models, at the steady-state level. The two general classes of such model, counter-and co-transport, can be treated by a kinetic analysis which makes no assumptions as to the symmetry or asymmetry of the systems nor as to the presence of any particular rate-limiting steps. Precisely the same formalism is obeyed for primary active transport as for secondary active transport. Both are merely a generalisation of facilitated diffusion, in that they follow directly from accepted properties of carrier models. How affinities of such carriers for their substrates affect the efficiency of active transport is discussed and it is shown that in a number of cases, the affinity changes that the carrier demonstrates arise from inherent properties of the free carrier and not from any "high energy" properties of the chemical reactants. Methods of obtaining the kinetic parameters of the system from experimental data are reviewed, together with methods for testing and characterising the different transport models.

The physical state of water and ions in living cells and a new theory of the energization of biological work performance by ATP.

Abstract: In this article, the key concepts of the association-induction hypothesis and their experimental verifications were reviewed: According to this hypothesis, the bulk of cell water exists in the state of multilayers polarized and oriented by the backbones of certain proteins existing in an extended state. The major intracellular cation, K+, is also adsorbed but singly and on different protein sites (i.e.,β &γ-carboxyl groups). The living protoplasm of protein, ion and water represents a three-dimensional cooperative assembly under the control of certain cardinal adsorbents, of which ATP is a prime example. Association of ATP with the cardinal site of a key protein may produce a cooperative change in the electron distribution of the protein with consequent change of the state of ion and water adsorption. Such an alteration in the physical state of water leads to a change in the solubility of various solutes in this water as well as permeability of various solutes (e.g., Na) through this water. In contrast to the conventional concept, the role of ATP is not to provide a package of energy held in a special chemical bond. Rather, as a cardinal adsorbent, ATP acts by means of its specific electronic interaction with the protein molecules, maintaining the protein—ion—water system at a higher energy state. Dephosphorylation of ATP leads to a cooperative shift of the electron state of the whole assembly to a lower energy state. Restoration to the original resting state follows the resynthesis of ATP (where energy is injected into the system) and its readsorption on the cardinal site. Living cells typically reside in a liquid environment. The discontinuity of the cell interior from the external milieu, essential for the normal functioning of the living cell, has long been a subject of central interest in mechanistic biology. Prominent in this discontinuity is the much higher concentration of K+ and much lower concentration of Na+ in the cell interior than in the cell environment, seen in virtually all living cells. We shall begin the present article with a discussion of the subject.

Cytoduction as a new tool in studying the cytoplasmic heredity in yeast

Abstract: When crossing the haploid cells of genetically marked yeast strains we observed the appearance of both normal diploid zygotes and haploid nuclear cytoplasmic hybrids The latter had the nuclear markers of one and the cytoplasmic marker (rho+) of the other parent The autonomous cytoplasmic factor transfer was termed as cytoduction Cytoduction is supposed to be the abortive form of yeast cell mating Only about 1% of cytoductants in usually observed Cytoduction can be used as a simple test on cytoplasmic determination of some characters We observed the transfer into cytoductant cells of not only rho+ marker but of resistance factors to antibiotics (erythromycin, neomycin) and killer factor as well Cytoduction can be applied towards constructing strains having the identical nucleus genotype with mitochondria and other cytoplasmic factors of different origin In crossing strains with doubly marked mitochondria recombination of mitochondrial markers in cytoductant haploid cells was observed, the pattern of which was similar to that of mitochondrial recombination in normal zygotes

The generation of the proton electrochemical potential and its role in energy transduction.

Abstract: The evidence that all energy transducing membranes can generate a proton electrochemical potential difference, Δ $$\tilde \mu $$ H, across the membrane and that this potential can be used to transfer energy among energy transducing units and to generate ATP, has increased the interest for the view that Δ $$\tilde \mu $$ H plays an obligatory role in energy transduction and ATP synthesis. In the present article we shall concentrate on two experimental questions related with the generation and role of Δ $$\tilde \mu $$ H: (a) the charge/site ratio; (b) the relation between the proton electrochemical potential on one side and the cation electrochemical potential, the phosphate potential and the redox potential on the other. We shall then discuss the view that energy transduction corresponds to a molecular energy machine rather than to a fuel cell.

An inverse relation between mitochondrial hexokinase content and phosphoglucomutase activity of rat tissues.

Abstract: The hexokinase: fumarase ratios of mitochondria isolated from ten tissues of the rat were determined, and compared with the tissue content of phosphoglucomutase and phosphorylase, taken as representatives of enzymes concerned with glycogen metabolism. A generally inverse relationship was found between the mitochondrial hexokinase: fumarase ratio and phosphoglucomutase levels. The cytochrome: fumarase ratios were relatively invariant in these same mitochondria. The results are interpreted as indicating a specialization of mitochondria, with increased amounts to hexokinase being associated with the mitochondria in tissues exhibiting less dependence on glycogen metabolism, as judged from phosphoglucomutase levels.

Glutamate dehydrogenases from Chlorella: forms, regulation and properties.

Abstract: Despite the great physiological importance of glutamate dehydrogenases (GDHs) fromChlorella, practically no pertinent data were available until 1965. We made an attempt to fill the gap and to determine the forms of GDH present inChlorella cells, the dependence of their synthesis on the nitrogen source, their physico-chemical and kinetic properties and their functional features in the cell. The thermophilic strainChlorella pyrenoidosa Pringsheim 82 T was selected for this purpose because it was shown to have both NAD- and NADP-GDH activities, the NADP-GDH activity being much higher under conditions of NH 4 + assimilation than in NO 3 - assimilation. Our findings allow the following conclusions to be made:

Purification and properties of alpha-amylase from chicken (Gallus gallus L.) pancreas.

Abstract: Amylase from chicken pancreas was purified by an affinity method involving filtering a crude extract from pancreas through a Sepharose-wheat albumin column and eluting the retained enzyme with maltose. The purified amylase showed two active bands upon polyacrylamide electrophoresis in an alkaline buffer system and only one band in an acidic buffer system. The enzyme is a Ca2+—glycoprotein which behaves as a typicalα-amylase. It consists of a single polypeptide chain with molecular weight 53,000 and contains 5.3 moles of reducing sugars per mole of protein. Optimal conditions of pH and temperature for the enzymic activity are 7.5 and 37°C. The enzyme is irreversibly inactivated by removal of Ca2+ by exhaustive dialysis and is activated by the presence in the assay mixture of Cl−; other halides are less effective than Cl− in activating the enzyme.

Trisialoganglioside synthesis by a chicken brain sialyltransferase. Comparative study with the similar reaction for the synthesis of disialoganglioside.

Abstract: An enzyme preparation from embryonic chicken brain catalyzes the transfer of sialic acid from CMP-N-acetylneuraminic acid to ceramide-Glc-Gal(NeuAc-NeuAc)-GalNAc-Gal (GDlb) to form ceramide-Glc-Gal(NeuAc-NeuAc)-GalNAc-Gal-NeuAc (GTlb). The sialyltransferase activity was measured during the development of the embryo, the subcellular distribution of this activity was determined and several kinetic properties of the reaction were ex-amined. A comparative study with the similar reaction involved in the transfer of sialic acid to the terminal galactose in ceramide-Glc-Gal(NeuAc)-GalNAc-Gal (GMl) was made. The results obtained in this comparative study suggest that the transfer of sialic acid in both reactions is catalyzed by the same enzyme.

Polyamines, ribonucleases, and the stability of RNA.

Abstract: The polyamines influence the activity of many enzymes involved in the synthesis and degradation of RNA. These organic cations (putrescine, spermidine, spermine) stimulate, for example, many DNA-dependent RNA polymerases and affect both RNA chain elongation and initiation. The polyamines also bind to polynucleotides, forming complexes having, in many cases, physical properties quite distinct from the parent polymer. Some of these complexes are resistent to ribonuclease mediated hydrolysis. However, polyamines alter the activity, as well as the specificity of some RNases, so the actual rate of breakdown of RNA is dependent on the interaction of polyamine with both RNA and enzyme. The hydrolytic rate may also be controlled by the presence of purine homopolymer, which acts to strongly inhibit RNase activity. The addition of polyadenylic acid tracts to the 3′ terminus of the RNA substrate, for example, protects the unpolyadenylated portion of the RNA molecule from degradation. Longer segments of poly(A) are more effective in this respect; however, regardless of poly(A) length, low concentrations of spermidine reverse the inhibition of RNase activity, with concomitant rapid degradation of the unpolyadenylated portion of the RNA molecule. Thus, RNA degradation depends not only on the presence of RNase, but on poly(A) length and spermidine concentration as well. Although the relative importance, within the cell, of each of these interactions is not known, the above mechanisms illustrate certain of the complexities and interrelations that may exist for the synthesis and, in particular, the RNase mediated degradation of RNA.

Carbohydrate composition of purified human liver alpha-L-fucosidase.

Abstract: Human liver α-L-fucosidase was purified to apparent homogeneity and analyzed for carbohydrate content primarily by gas-liquid chromatography (glc). The enzyme is about 7% carbohydrate by weight and contains the following sugars (residues per 50,000 molecular weight subunit): mannose (8.3), glucosamine (4.3) (presumably N-acetylated), sialic acid (1.6) and glucose (1.6). Galactose (0.8) and L-fucose (1.8) were also found but their presence may be due to artifacts of the purification procedure.

Sucrose metabolism in green algae. I. The presence of sucrose synthetase and sucrose phosphate synthetase.

Abstract: The presence of sucrose synthetase and sucrose phosphate synthetase has been demonstrated in two species of green algae: Chlorella vulgaris and Scenedesmus obliquus Partial purification from crude extracts allowed the determination of the kinetic constants of algae enzymes They are very similar to the ones reported for enzymes from higher plants

Purification and biochemical studies of lactate dehydrogenase-X from mouse.

Abstract: Lactate dehydrogenase-X from testes of several rodent species was purified to homogeneity by an 8-(6-aminohexyl)-amino-AMP-Sepharose affinity column. In the case of mouse, the testicle extracts was first heated to 60° for fifteen minutes before the passage through the affinity column. A biospecific elution with reduced NAD+-pyruvate adduct resulted in a homogeneous preparation of lactate dehydrogenase-X. A similar procedure was also employed for the purification of lactate dehydrogenase-X from hamster, guinea pig and rat. After purification by affinity chromatography, lactate dehydrogenase-X was separated from residual somatic lactate dehydrogenase isozymes by DEAF-Sephadex chromatography. Adenosine, AMP, ADP, and ADP-ribose were shown to be coenzyme-competitive inhibitors of lactate dehydrogenase-X. The effectiveness of binding of these compounds increased with the size of the adenosine derivatives employed. Multiple inhibition analysis suggested that these compounds are interacting with the same region of coenzyme-binding site as shown by the mutual exclusion of one another from binding to the enzyme. The data suggest that the binding of coenzyme to the enzyme occurs through interactions involving the adenosine moiety and pyrophosphate grouping. Fluorescence spectroscopy was employed for the study of the mechanism of action of mouse lactate dehydrogenase-X. Both oxidized and reduced coenzymes induced significant quenching of protein fluorescence. Significant enhancements of NADH fluorescence and protein energy transfer were observed upon the addition of lactate dehydrogenase-X to the coenzyme solution. In the presence of lactate dehydrogenase-X and NAD+, the addition of pyruvate or α-ketovalerate resulted in a time-dependent quenching of protein fluorescence and an increase in absorbance at 325 nm indicating the formation of a ternary complex. The results of this study suggest a similar molecular mechanism for different lactate dehydrogenase isozymes.

Glycosylation of endogenous protein(s) of the rough and smooth microsomes by a lipid sugar intermediate.

Abstract: Several problems regarding the protein acceptor of the oligosaccharide from GEA (glucosylated endogenous acceptor) were investigated in the present work using rat liver microsomal subfractions. It was found that the acceptor molecule is present in rough and smooth liver microsomes. Furthermore both fractions have closely similar specific activities. The problem of whether nascent peptides must be ribosome bound for glycosylation to occur was studied. The results suggests that binding of peptides to ribosomes is not a necessary condition for the transfer of GEA oligosaccharide to protein. The increase in specific activity found after partial release of the microsomal vesicular content suggests that the acceptor protein for GEA is membrane bound. Evidence obtained in attempting to elucidate whether nascent or completed chains are glycosylated favours the later possibility.

Preparation and characterization of isolated parenchymal cells from guinea pig liver.

Abstract: 1. A method is described for the preparation of isolated cells from guinea pig liver. This involves perfusionin situ, in the non-physiological direction, with collagenase. 2. The cell yield was 20-30%, comparable with those from the livers of other species. 3. The ratio of lactate dehydrogenase to glutamate dehydrogenase in the cells was similar to thatin vivo, indicating that there was negligible leakage of cytoplasmic enzymes. 4. The concentrations of K+ and adenine nucleotides were initially lower than in the perfused liver; normal values were obtained on incubation, particularly in the presence of substrate. 5. The L-lactate : pyruvate ratio is 16 : 1, close to established values. The totalβ-hydroxybutyrate : acetoacetate ratio indicates that the mitochondrial redox state is more oxidised than in the perfused liver, but the intracellular ratio is similar to that of the intact liver. 6. Rates of gluconeogenesis and ureogenesis, are within the physiological range. Maximal gluconeogenesis from L-lactate was preceded by a lag period. L-lysine stimulated glucose production from L-lactate but did not abolish the lag phase. 7. The effects of aminooxyacetate and octanoate on L-lactate gluconeogenesis were similar to those in the perfused liver.

Genetic determination of the mitochondrial adenine nucleotide translocation system and ITS role in the eukaryotic cell

Abstract: On integrating experimental data published previously, the following picture of the mitochondrial adenine nucleotide(AdN) translocation system is being presented:

Studies on the adrenal cortex of hypophysectomized rats: a model for abnormal cellular atrophy and death.

Abstract: Biochemical and ultrastructural studies indicate that the atrophy of adrenal cortex in hypoyhysectomized rats involves the following changes: (1) One to two days after hypophysectomy, there is loss of “template activity” resulting from cumulative DNA-damage and heterochromatinization.In vivo ACTH-administration led to recuperation of these cells, indicating damage during hypophysectomized state to be reversible. (2) If the duration of hypophysectomy is prolonged, some of the cells become irreversibly damaged and can no longer recuperate afterin vivo ACTH administration. (3) The period of most rapid cell death is from the third to seventh day after hypophysectomy. The cause of cell death is probably due to membrane damage in the absence of protein synthesis, leading to lysis of the cells. Lysozomes and macrophages are apparently not involved.

The ostrich (Struthio camelus) egg-white lysozyme.

Abstract: The purification of Ostrich (Struthio camelus) egg-white lysozyme is reported. The quantitative amino acid composition, the molecular weight, the N-terminal sequence (34 amino acids) as well as kinetic studies allow to range this enzyme among the goose type lysozymes.

Incorporation and metabolism of stearic, oleic, linoleic andα-linolenic acids in Minimal Deviation Hepatoma 7288 C cells

Abstract: Minimal Deviation Hepatoma 7288 C cells were cultured in confluent layer with labeled stearic, oleic, linoleic andα-linolenic acids. The kinetics of incorporation and conversion to higher homologs was studied. The maximum amounts incorporated in nmoles per mg of cellular protein for stearic, oleic, linoleic andα-linolenic acids were 39, 115.6, 90 and 230 respectively.α-linolenic acid was converted to octadeca-6,9,12,15-tetraenoic acid (18:4), eicosa-11,14,17-trienoic acid (20:3), eicosa-8,11,14,17 and 5,11,14,17-tetraenoic acids (20:4) and eicosa-5,8,11,14,17-pentaenoic acid (20:5), and also to myristic, palmitic, palmitoleic, stearic and oleic acids. By a mathematical approach, the endogenous pool size ofα-linolenic acid available for conversion to eicosa-5,8,11,14,17-pentaenoic acid, and the capacity of the cell to convertα-linolenic acid to eicosa-5,8,11,14,17-pentaenoic acid, were calculated. Both values decreased when the cells were preincubated with unlabeledα-linolenic acid.

A model for the interaction of wheat monomeric and dimeric protein inhibitors with alpha-amylase.

Abstract: The amylase-protein amylase inhibitor system offers a unique model of specific and reversible protein-protein interaction. The monomeric and dimeric inhibitors, exhibiting closely related properties and interacting with the same amylase, also provide a convenient test to compare effects of monomer-monomer and monomerdimer interactions between enzyme and inhibitor proteins.

The role of glutathione in renal cortical tissue. Effects of diamide on Na+ and GSSG levels, amino acid transport and Na+-K+-ATPase activity.

Abstract: The effects of diamide were studied in rat kidney cortical tissue. It was found that diamide increased oxidized glutathione levels and inhibited Na+-K+-ATPase activity. Consistent with this finding was the observation that diamide compromised the sodium gradients maintained in renal cortical slices. Amino acid transport studies with ouabain or a sodium-free buffer indicated that diamide interferes with both Na+-dependent and Na+-independent transport systems. These results indicate that diamide has a number of different effects on renal cortical tissue and emphasize the important role of glutathione in maintaining control of a number of key metabolic pathways.

Influence of 4′-6-diamidino-2-phenylindole on the secondary structure and template activities of DNA and polydeoxynucleotides

Abstract: The interaction between 4′-6-Diamidino-2-Phenylindole-hydrochloride (DAPI) and a variety of DNAs and synthetic polydeoxynucleotides was investigated in order to delineate the nucleic acid structural features necessary for binding. The spectra of DAPI-DNA complexes, measured at various DAPI-DNA molar ratios (r), are hypochromic relative to DNA in the region of its maximum absorption. All the curves pass through an isosbestic point at 268 nm. A new maxima appears in the region of 380–392 nm for DAPI-DNA complexes. The magnitude of the peaks in the region are directly proportional to the amount of drug present in the complex.

Cholestrol in muscle membranes

Abstract: The composition of skeletal muscle microsomes is reviewed. Evidence for the involvement of cholesterol in the transport of calcium by vesicles derived from the sarcoplasmic reticulum is considered. Results obtained by non aqueous extractions of skeletal muscle microsomes, and by use of the cholesterol analogue 20, 25 diazacholesterol indicate that cholesterol is not involved in calcium transport by vesicles of sarcoplasmic reticulum origin. Use of density perturbation procedures indicating that cholesterol is present in muscle membranes other than those of the sarcoplasmic reticulum involved in calcium transport is discussed. The distribution of membranal cholesterol is muscle is compared to that in other tissues.

Synthesis of polyprenol-monophosphate- beta -galactose by acetobacter xylinum.

Abstract: A particulate enzyme preparation fromAcetobacter xylinum synthesizes ficaprenol-monophosphate-β-galactose from ficaprenol monophosphate (FMP) and UDP-galactose in the presence of detergent. The product has the same properties as those previously reported for the compound formed with the endogenous acceptor. Dolichol-monophosphate (DolMP) is also a good galactose acceptor but the product obtained has different properties. Lipid extracts fromAcetobacter contain galactose acceptor capacity which is lost by mild acid treatment. FMP behaves in a similar manner but DolMP is resistant to this treatment. It is concluded that the endogeneous acceptor is an allylic phosphate ester of a polyprenol.

Polyamines and protein synthesis: Studies in various polyamine-requiring mutants ofEscherichia coli

Abstract: DifferentEscherichia coli mutants auxotrophic for polyamines were studied in order to investigate the relationships among polypeptide synthesis in cell-free systems, ribosomal distribution profiles and endogenous polyamine pools. Thein vitro protein synthetic activity and the polyribosomal content were reduced in extracts from putrescine-starved cells of the double mutants MA 255 and MA 261, but not in the arginine-conditional auxotroph DK 6. Putrescine addition to the cultures of all these strains previously starved for polyamines, provoked a shift towards monomers in the equilibrium involving ribosomal particles. Concomitant changes in the intracellular levels of polyamines were observed: putrescine and spermidine increased markedly, and cadaverine disappeared.