| the action of phenoxyethanol upon respiration and dehydrogenase enzyme systems in escherichia coli proceedings. | | 1976 | 12328 |
| formation of mutagenic n-nitroso compounds from the pesticides prometryne, dodine and carbaryl in the presence of nitrite at ph 1. | environmental chemicals including pesticides carrying secondary and tertiary amino groups are suggested to be a health hazard to man since potentially carcinogenic nitroso compounds may be formed in the presence of nitrite at low ph values resembling conditions in the human stomach. nitrosation of the isopropylamino-triazine prometryne, the n-dodecyl guanidine dodine and the n-methylcarbamate carbaryl was investigated in the presence of hcl and acetic acid at ph 1 and excess sodium nitrite for 4 ... | 1976 | 12468 |
| pola6, a mutation affecting the dna binding capacity of dna polymerase i. | the pola6 mutation is an allele of the pola gene of escherichia coli which produces a dna polymerase i species readily distinguishable from that produced by the wild type allele. experiments described here show that this enzyme has an altered ph optimum for polymerization and a lower binding affinity for dna. the defect clearly lies within the carboxyl-terminal large fragment of the enzyme produced by in vivo or in vitro proteolysis since the fragment has the same ph optimum for polymerization a ... | 1976 | 12497 |
| stabilization of an acetyl-coenzyme a carboxylase complex from pseudomonas citronellolis. | using stabilizing conditions the acetyl-coa carboxylase (ec 6.4.1.2) of pseudomonas citronellolis has been isolated as a complex containing four different polypeptide chains with molecular weights of 53 000, 36 000, 33 000 and 25 000. evidence is presented to suggest that these polypeptide chains correspond to distinct biotin carboxylase, transcarboxylase and biotin carboxyl carrier protein subunits in analogy with similar subunits of escherichia coli acetyl-coa carboxylase, an unstable complex ... | 1976 | 12801 |
| differential, structure-dependent susceptibility of poly(a) and rna to monomeric and dimeric pancreatic ribonuclease a. | cross-linked dimers of bovine rnaase a are definitely more efficient than monomers at degrading polyadenylic acid under conditions of ionic strength and ph, where the polymer assumes either a double-helical or an ordered single-stranded, base-stacked structure. the opposite occurs, i.e., monomers of rnaase a are definitely more active than dimers,when poly(a) is digested by the two enzyme species under conditions where the conformation of the polymer is essentially that of a random coil. the sam ... | 1977 | 12819 |
| metal ion-induced conformational changes in escherichia coli alkaline phosphatase. | ultraviolet difference spectra are produced by the binding of divalent metal ions to metal-free alkaline phosphatase (ec 3.1.3.1). the interaction of the apoprotein with zn2+, mn2+, co2+ and cd2+, which induce the tight binding of one phosphate ion per dimer, give distinctly different ultraviolet spectra changes from ni2+ and hg2+ which do not induce phosphate binding. spectrophotometric titrations at alkaline ph of various metallo-enzymes reveal a smaller number of ionizable tyrosines and a gre ... | 1977 | 12823 |
| a cis-trans isomerising activity of escherichia coli. isomerization from 2-(2-furyl)-3-cis-(5-nitro-2-furyl) acrylamide (furylfuramide) to its trans isomer. | the soluble enzyme fraction derived from escherichia coli k-12 je2100 cells was found to exhibit, in addition to nadh- and nadph-dependent reductase activities, nadh-dependent cis-trans isomerising activity toward 2-(2-furyl-3-(5-nitro-2-furyl)acrylamide leading to a specific change in geometrical configuration of the vinyl group at the 2-position from cis to trans but not in the reverse direction. this furylfuramide-isomerising action of bacteria was dicoumarol insensitive, and did not require ... | 1977 | 12827 |
| studies on the biosynthesis of acylphosphatidylglycerol in escherichia coli b and b/r. | the present study has demonstrated that one molecule of acylphosphatidylglycerol was synthesized from two molecules of phosphatidylgycerol by the transacylation reaction in which phosphatidylglycerol acted both as an acyl donor and an acceptor. phosphatidylethanolamine was identified as an another acyl donor, participating in acylphosphatidylglycerol formation. these results are discussed in terms of a new pathway for the turnover of phosphatidylglycerol in escherichia coli. | 1976 | 12836 |
| enzyme reduction of disulfide bonds by thioredoxin. the reactivity of disulfide bonds in human choriogonadotropin and its subunits. | the nadph-dependent enzymic reduction of disulfide bonds in human choriogonadotropin and its two subunits, alpha and beta, was examined with thioredoxin and thioredoxin reductase from escherichia coli. with 12 mum thioredoxin and 0.1 mum thioredoxin reductase at ph 7 all disulfide bonds in the alpha subunit could be reduced in 15 min. the reduction of disulfide bonds was recorded by a simple spectrophotometric assay at 340 nm, which allowed quantitation of the reduction rate and the number of di ... | 1976 | 12950 |
| studies on 3-deoxy-d-arabinoheptulosonate-7-phosphate synthetase(phe) from escherichia coli k12. 1. purification and subunit structure. | 1. 3-deoxy-d-arabinoheptulosonate-7-phosphate synthetase(phe) from escherichia coli k12 has been purified to near homogeneity. the purified enzyme has a specific activity of 67 units/mg which is about 1000 times that found in cell-free extracts of wild-tupe e. coli k12. 2. the minimum molecular weight of the enzyme was estimated by dodecylsuphate-gel electrophoresis to be 33000. re-estimation of the native molecular weight by gel filtration confirmed the previously determined value of 110000. 3. ... | 1976 | 12951 |
| studies on 3-deoxy-d-arabinoheptulosonate-7-phosphate synthetase(phe)from escherichia coli k12. 2. kinetic properties. | 1. co2+ is not a cofactor for 3-deoxy-d-arabinoheptulosonate-7-phosphate synthetase(phe). 2. the following analogues of phosphoenolpyruvate were tested as inhibitors of 3-deoxy-d-arabinoheptolosonate-7-phosphate synthetase(phe): pyruvate, lactate, glycerate, 2-phosphoglycerate, 2,3-bisphosphoglycerate, 3-methylphosphoenolpyruvate, 3-ethylphosphoenolpyruvate and 3,3-demethylphosphoenolpyruvate. the rusults obtained indicate that the binding of phosphoenolpyruvate to the enzyme requires a phosphor ... | 1976 | 12952 |
| studies on 3-deoxy-d-arabinoheptulosonate-7-phosphate synthetase(phe) from escherichia coli k12. 3. structural studies. | 1. investigations with structural analogues of phenylalanine indicated an absolute requirement for the aromatic ring and both the alpha-carboxyl and alpha-amino groups of phenylalanine for inhibition of 3-deoxy-d-arabinoheptulosonate-7-phosphate synthetase(phe) activity. replacement of the alpha-h atom with a methyl group does not decrease the inhibition greatly. varying degrees of inhibition were observed with o, m and p mono-substituted fluoro, chloro and hydroxy phenylalanines. d-phenylalanin ... | 1976 | 12953 |
| interaction of dna with dna-binding proteins. the characterization of protein hd from escherichia coli and its nucleic acid complexes. | dna-binding protein hd with a monomer molecular weight of 9000 was isolated from escherichia coli cells. the protein occurs as a tetramer under native conditions and binds to single and double-stranded dna and also to rna. dna complexed with protein hd is a poor template for dna synthesis by e. coli polymerase i, ii or iii holoenzyme. exonuclease iii is hindered in degrading hd-protein-covered double-stranded dna, whereas exonuclease i can digest complexed single-stranded dna. transcription is l ... | 1976 | 12966 |
| role of urinary solutes in natural immunity to gonorrhea. | natural resistance of the male urethra to gonococci has not been explained by classical immune mechanisms but could result from antibacterial properties of urine. accordingly, we measured survival in midmorning urine of 10(7) f-62 t2 gonococci per ml by serial dilutions and plate counts. fifteen killer urines from eight people all killed greater than 3 logs (average, 5.3), and 13 of 15 were sterilized. fourteen nonkiller (inhibitor) urines from seven subjects allowed no growth. killer urines wer ... | 1977 | 13038 |
| a dipeptidase from escherichia coli b. | | 1976 | 13264 |
| dipeptidyl carboxypeptidase from escherichia coli. | | 1976 | 13271 |
| biochemical, genetic, and regulatory studies of alanine catabolism in escherichia coli k12. | e. coli k12 was found to utilise both d-and l-stereoisomers of alanine as sole sources of carbon, nitrogen and energy for growth. this capability was absolutely dependent upon the possession of an active membrane-bound d-alanine dehydrogenase, and was lost by mutants in which the enzyme was defective. the michaelis constant for the enzyme with d-alanine as substrate was 30 mm, and the ph optimum about 8.9. d-alanine was the most active substrate, l-alanine was inactive and several other d-amino ... | 1976 | 13292 |
| methylation and aging in rhizoctonia solani. | our earlier studies had shown that as fungi age, many of their vital functions decrease; in rhizoctonia solani, protein synthesis is one of the functions so affected. we now find that the ability to methylate trna, a vital component of the protein synthesizing system, also decreases with age. this methylation of escherichia coli trna by r. solani methylase preparations increased with the concentration of enzyme and with time of incubation; in both cases the rate of increase was considerably high ... | 1976 | 13305 |
| hydrolysis of lactose by immobilized microorganisms. | cells of lactobacillus bulgaricus, escherichia coli, and kluyveromyces (saccharomyces) lactis immobilized in polyacrylamide gel beads retained 27 to 61% of the beta-galactosidase activity of intact cells. optimum temperature and ph and thermostability of these microbial beta-galactosidases were negligibly affected by the immobilization. km values of beta-galactosidase in immobilized cells of l. bulgaricus, e. coli, and k. lactis toward lactose were 4.2, 5.4, and 30 mm, respectively. neither inhi ... | 1977 | 13709 |
| purification and characterization of the inactive ca2+, mg2+-activated adenosine triphosphatase of the unc a- mutant escherichia coli an120. | | 1977 | 13731 |
| d-alanine dehydrogenase. its role in the utilisation of alanine isomers as growth substrates by pseudomonas aeruginosa pa01. | pseudomonas aeruginosa pa01 was found to utilise both the d- and l-isomers of alpha-alanine and also beta-alanine as sole sources of carbon and energy for growth. enzymological studies of wild-type cultures and comparison with mutants deficient in growth upon one or more isomers of alanine led to the following conclusions: (i) utilisation of d-alanine involved its direct oxidation by an inducible, membrane-bound, cytochrome-linked dehydrogenase; (ii) utilisation of l-alanine required its convers ... | 1976 | 13755 |
| isolation, characterization, and activation of the magnesium dependent endodeoxyribonuclease from bacillus subtilis. | a major endodeoxyribonulcease was isolated from a mutant of the transformable bacillus subtilis 168. the magnesium-dependent endonuclease was purified approximately 750-fold to electrophoretic homogeneity. the enzyme had a molecular weight of about 31 000, as determined by gel filtration and polyacrylamide gel electrophoresis. the protein appears to be composed of two subunits. the nuclease was dependent on magnesium or maganese ions for hydrolytic activity. the purified nuclease degraded dna fr ... | 1977 | 13815 |
| effect of magnesium on the properties of zinc alkaline phosphatase. | alkaline phosphatase of escherichia coli, isolated by procedures which do not alter its intrinsic metal content, contains 4.0 +/- 0.3 g-atoms of tightly bound zinc per mole (kd less than 1 mum) and 1.3 +/- 0.2 g-atoms of magnesium per mole (bosron, w.f., kennedy, f.s., and vallee, b.l. (1975), biochemistry 14, 2275-2282). importantly, the binding of magnesium is dependent both upon ph and zinc content. hence, the failure to assign the maximal magnesium stoichiometry to enzyme isolated by convent ... | 1977 | 13822 |
| a specific polyadenylase from escherichia coli k12. | a polyadenylase, degrading specifically poly(a) sequences was isolated from escherichia coli k12. the enzyme was purified about 850 times to practically electrophoretic homogeneity. it was free of poly(a) polymerase activity, as well as of the well known e. coli rnaases i and ii. it is stimulated by bivalent cations like mg2+ and mn2+ and splits poly(a) to 3'-amp and therefore it can be considered as an exonuclease. the enzyme does not degrade any other ribohomopolymer or rna. | 1977 | 13837 |
| studies on aspartase. iv. reversible denaturation of escherichia coli aspartase. | aspartase (l-aspartate ammonia lyase, ec 4.3.1.1) of escherichia coli, denatured in 4 m guanidine-hcl, was renatured in vitro by simple dilution with a concomitant restoration of the activity. while the native enzyme exhibited a marked negative cotton effect centered at 233 +/- 1 nm in optical rotatory dispersion, the enzyme denatured in 4 m guanidine-hcl retained little optical activity. upon dilution of the denatured enzyme, however, more than 90% of the ordered structure was recovered in 1 mi ... | 1977 | 13846 |
| hnmr of succinate binding to aspartate transcarbamylase. a comparison of results in d2o and h2o. | the interaction of succinate with asparatete transcarbamylase from escherichia coli has been studied by magnetic resonance relaxation measurements of the dicarboxylic acid methylene protons in h2o solutions. the ph and temperature dependence of the relaxation in the presence of either native asparte transcarbamylase or its catalytic subunit in h2o solutions is qualitatively very similar to the corresponding situation utilizing d2o as the solvent. from previous result of measurements in d2oc.b. ... | 1976 | 13874 |
| detergent-resistant phospholipase a of escherichia coli k-12. purification and properties. | detergent-resistant phospholipase a, which is tightly bound to the outer membranes of escherichia coli k-12 cells, was purified approximately 2000-fold to near homogeneity by solubilization with sodium dodecylsulfate and butan-1-ol, acid precipitation, acetone fractionation and column chromatographies on sephadex g-100 in the presence of sodium dodecylsulfate and on deae-cellulose in the presence of triton x-100. the final preparation showed a single band in the sodium dodecylsulfate gel system. ... | 1977 | 14002 |
| polypeptide chain stoicheiometry in the self-assembly of the pyruvate dehydrogenase multienzyme complex of escherichia coli. | | 1977 | 14024 |
| biochemical parameters of glutamine synthetase from klebsiella aerogenes. | the glutamine synthetase (gs) from klebsiella aerogenes is similar to that from escherichia coli in several respects: (i) it is repressed by high levels of ammonia in the growth medium; (ii) its biosynthetic activity is greatly reduced by adenylylation; and (iii) adenylylation lowers the ph optimum and alters the response of the enzymes to various inhibitors in the gamma-glutamyl transferase (gammagt) assay. there are, however, several important differences: (i) the isoactivity point for the ade ... | 1977 | 14104 |
| adenosine 5'-triphosphate synthesis driven by a protonmotive force in membrane vesicles of escherichia coli. | adenosine 5'-triphosphate (atp) synthesis energized by an artificially imposed protonmotive force (delta p) in adenosine 5'-diphosphate-loaded membrane vesicles of escherichia coli was investigated. the protonmotive force is composed of an artificially imposed ph gradient (delta ph) or membrane potential (deltapsi), or both. a delta ph was established by a rapid alteration of the ph of the assay medium. a delta psi was created by the establishment of diffusion potential of k+ in the presence of ... | 1977 | 14110 |
| isolation of an escherichia coli mutant deficient in thioredoxin reductase. | a mutant of escherichia coli defective in thioredoxin reductase has been isolated and partially characterized. this mutant has no detectable thioredoxin reductase activity in vitro and yet it exhibits no in vivo defect in reduction of ribonucleotides. evidence is presented that indicates that, in cells permeabilized via ether treatment, ribonucleoside diphosphate reduction can utilize glutathione as an alternate reducing system. | 1977 | 14115 |
| interactions of outer membrane proteins o-8 and o-9 with peptidoglycan sacculus of escherichia coli k-12. | the outer membrane proteins o-8 and o-9 were specifically bound to the peptidoglycan sacculus in sodium dodecyl sulfate (sds) solution. other cellular proteins failed to interact with the peptidoglycan sacculus under the same conditions. when the outer membrane was preheated in sds solution, the binding did not take place. optimum binding was observed at ph 8 in the presence of 5 mm mg2+. a high concentration of sodium chloride strongly inhibited the binding. the effects of these factors on the ... | 1976 | 14126 |
| alteration of the kinetic parameters for aminoacylation of escherichia coli formylmethionine transfer rna by modification of an anticodon base. | treatment of escherichia coli formylmethionine trna with 2 m sodium bisulfite, ph 7.0, in 10 mm mgcl2 at 25 degrees results in formation of uridine/bisulfite adducts at u18 in the dihydrouridine loop, u37 in the anticodon, and u48 in the variable loop. two products, corresponding to the two diastereoisomers of 5,6-dihydrouridine-6-sulfonate, are formed at each reactive site in the trna. although none of the modifications cause complete loss of methionine acceptor activity, the modified trna is a ... | 1977 | 14133 |
| endonuclease v of escherichia coli. | a small endodeoxyribonuclease )2.3 s) that is active on single-stranded dna has been extensively purified from escherichia coli so as to be free of other known dnases. it has an alkaline ph optimum (9.5), requires mg2+, and makes 3'-hydroxy and 5'-phosphate termini. the nuclease nicks duplex dna, particularly if treated with oso4, irradiated with ultraviolet light, or exposed to ph 5. the uracil-containing duplex dna from the bacillus subtilis phage pbs-2 is an especially good substrate; it is m ... | 1977 | 14159 |
| fluoresceinylthiocarbamyl-trnatyr: a useful derivative of trnatyr (e.coli) for physicochemical studies. | fluoresceinylthiocarbamyl-trnatyr (ftc-trnatyr) is prepared from trnatyr and fluoresceinisothiogyanate (fitc) under mildly alkaline conditions. labelling occurs specificly at the base q of trnatyr. the modified trna is fully active in the aminoacylation assay; when aminoacylated it is recognized by the elongation factor tu (ef-tu). codon-anticodon interaction, however, is severely affected by the modification. | 1977 | 14327 |
| studies on the mechanism of interaction of glutaraldehyde with microorganisms (author's transl). | the antimicrobial action of glutaraldehyde on candida lipolytica increases with reagent concentration, ph and duration of contact. the simultaneous study of the size distribution of the particles shows an agglutination of the cells. this result is confirmed by direct observation of the cells by electron microscopy. cell agglutination also occurs with other microorganisms (saccharomyces carlsbergensis, bacillus megaterium, escherichia coli) and increases their settling rate. the formation of such ... | 1976 | 14579 |
| the electrochemical proton gradient in escherichia coli membrane vesicles. | membrane vesicles isolated from escherichia coli grown under various conditions generate a transmembrane ph gradient (delta ph) of about 2 ph units (interior alkaline) under appropriate conditions when assayed by flow dialysis. using the distribution of weak acids to measure delta ph and the distribution of the lipophilic cation triphenylmethylphosphonium to measure the electrical potential (delta psi) across the membrane, the vesicles are demonstrated to develop an electrochemical proton gradie ... | 1977 | 14664 |
| the relationship between the electrochemical proton gradient and active transport in escherichia coli membrane vesicles. | in the previous paper ramos, s., and kaback, h.r. (1977), biochemistry 16 (preceding paper in this issue), it was demonstrated that escherichia coli membrane vesicles generate a large electrochemical proton gradient (delta-muh+) under appropriate conditions, and some of the properties of delta-muh+ and its component forces i.e., the membrane potential (delta psi) and the chemical gradient of protons (deltaph) were described. in this paper, the relationship between delta-muh+, delta psi, and delt ... | 1977 | 14665 |
| selective chemical modification of escherichia coli elongation factor g: butanedione modification of an arginine essential for nucleotide binding. | treatment of escherichia coli elongation factor g with the arginine reagent, 2,3-butanedione, leads to the inactivation of the enzyme when performed in sodium borate buffers. the inhibition follows pseudo-first-order kinetics until 95% of the activity has been lost and further incubation results in complete inhibiton. removal of the borate by exhaustive dialysis results in the restoration of approximately 85% of the original activity. the ph dependence of the reaction suggests that the ionizatio ... | 1977 | 14679 |
| a mutant atp synthetase of escherichia coli with an altered sensitivity to n,n' -dicyclohexylcarbodiimide: characterization in native membranes and reconstituted proteoliposomes. | dicyclohexylcarbodiimide-resistant mutants of escherichia coli were isolated and characterized in one mutant the unc genes and affects the membrane-integrated part of the atp synthetase. the sensitivity of atp synthetase functions to n,n' -dicyclohexylcarbodiimide was compared in wild-type and mutant membranes. the membrane-integrated part of the wild-type atp synthetase is highly sensitive to atp-dependent membrane energization and restoration of lactate-dependent energization of atpase-deplete ... | 1977 | 14831 |
| bacteriostatic effect of human milk and bovine colostrum on escherichia coli: importance of bicarbonate. | at ph 7.4 and in the presence of nahco3, human milk and bovine colostrum inhibited the growth of escherichia coli o111. adding sufficient iron to saturate the iron-binding capacity of the lactoferrin present in the milk or colostrum prevented bacteriostasis. at ph 6.8 neither molk nor colostrum inhibited e. coli 0111. adjusting the ph to 7.4 with nahco3 resulted in the development of bacteriostatic activity. adjusting the ph to 7.4 with naoh was ineffective. dialyzed colostrum and milk inhibited ... | 1977 | 14890 |
| iodinated radiological contrast media as radiosensitizers. | this paper describes the radiosensitizing effects of diatrizoic (da) and iothalamic (ita) acids and of iodipamide (ip) on the survival of e coli b/r irradiated with x-rays and with high-intensity electron pulses. all compounds at concentrations between 10 and 50 mm display a strong sensitizing effect in the presence of oxygen (dmf between 0-1 and 0-3) and are much less effective in nitrogen. in n2o the degree of sensitization is intermediate between oxygen and nitrogen. the situation is the same ... | 1977 | 14900 |
| partial purification of the escherichia coli k-12 mec+ deoxyribonucleic acid-cytosine methylase: in vitro methylation completely protects bacteriophage lambda deoxyribonucleic acid against cleavage by r-ecorii. | a procedure is described for the partial purification of the deoxyribonucleic acid (dna)-cytosine methylases controlled by the rii plasmid and by the escherichia coli mec+ gene. the two enzymes exhibit similar but distinct chromatographic behavior on diethylaminoethyl-cellulose and phosphocellulose. preliminary studies on the two methylases indicate that they are indistinguishable with respect to their km for s-adenosylmethionine and their ph (in tris (hydroxymethyl)aminomethane buffer) and nacl ... | 1977 | 14921 |
| ornithine transcarbamylase from salmonella typhimurium: purification, subunit composition, kinetic analysis, and immunological cross-reactivity. | ornithine transcarbamylase (otcase) was purified to hemogeneity from a derepressed strain of salmonella typhimurium. the optimal ph for enzyme activity is 8.0. the molecular weight of the enzyme was calculated to be 116,000, based on measurements of the sedimentation coefficient by sucrose gradient ultracentrifugation and the stokes radius by gel filtration. polyacrylamide gel electrophoresis of cross-linked otcase in the presence of sodium dodecyl sulfate showed that the enzyme is composed of t ... | 1977 | 14923 |
| nucleoside triphosphate phosphohydrolase associated with cytoplasmic polyhedrosis virus. | nucleoside triphosphate phosphohydrolase ec 3.6.1.15 activity was found to be included in silkworm cytoplasmic polyhedrosis (cp) virus, which synthesizes mrna carrying the 5'-terminal modification. this enzyme releases orthophosphate from the gamma-position in a nucleoside triphosphate, leaving nucleoside diphosphate. the rate of hydrolysis of atp is faster than that of any other ribonucleoside triphosphate. deoxy atp is hydrolyzed rather faster than atp. however, polynucleotides carrying tripho ... | 1977 | 14944 |
| proton magnetic relaxation of aspartate transcarbamylase - succinate complexes. | nuclear magnetic relaxation methods were used to investigate the interaction of the inhibitor succinate with aspartate transcarbamylase from escherichia coli. over the ph range 7 to 9, the dissociation constant for succinate remains less than the inhibitor concentration used for most of this work (0.05 m). as a result, the enzyme predominantly exists in a single "gross" conformational state. succinate binding to this enzyme state (generally known as the r form) parallels the behavior seen previo ... | 1977 | 14960 |
| two distinct types of trimethoprim-resistant dihydrofolate reductase specified by r-plasmids of different compatibility groups. | r-plasmids from a number of trimethoprim-resistant escherichia coli and citrobacter sp. were studied after transfer to e. coli k12 hosts. each was found to specify a dihydrofolate reductase which was resistant to trimethoprim and methotrexate, and which could be completely separated from the host chromosomal enzyme by gel filtration. two distinct types of r-plasmid dihydrofolate reductases were identified. type i enzymes, typified by the r483 enzyme previously described (sköld, o., and widh, a. ... | 1977 | 14961 |
| a protonmotive force as the source of energy for galactoside transport in energy depleted escherichia coli. | an artificially produced electrochemical potential difference for protons (portonmotive force) provided the energy for the transport of galactosides in escherichia coli cells which were depleted of their endogenous energy reserves. the driving force for the entry of protons was provided by either a transmembrane ph gradient or a membrane potential. the ph gradient across the membrane was created by acidifying the external medium. the membrane potential (inside negative) was established by the ou ... | 1977 | 15125 |
| interaction of transfer rna with 50s ribosomal subunits of escherichia coli in absence of templates. | the equilibrium constant of a complex of trna with the 50s ribosomal subunit was measured in the absence of a template. it was shown that the stability of the complex increases with an increase in the concentration of mg2+, it decreases with an increase in the concentration of univalent ions, and does not depend on the ph of the medium in the range of 7.0-8.2. removal of the 3'-terminal nucleoside of trna weakens the association approximately 40-fold; the subsequent successive splitting off of a ... | 1976 | 15209 |
| acceptor activity of trnaphe from yeasts under special conditions of aminoacylation. | the reaction of aminoacylation of trnaphe from yeasts and the erroneous acylation of total trna from e. coli by yeast phenylalanyl-trna synthetase under special conditions was studied. it was shown that the decrease in the degree of acylation of trnaphe and the increase in the degree of erroneous acylation of the total trna from e. coli are associated with the influence of these conditions on the structure of trna, and not on the structure or specificity of the enzyme. it was found that under sp ... | 1976 | 15212 |
| membrane-associated assembly of m13 phage in extracts of virus-infected escherichia coli. | assembly of coliphage m13 is known to occur as the viral dna crosses the cytoplasmic membrane, shedding its virus-coded dna unwinding protein and acquiring from the membrane approximately 2400 copies of the major coat protein. conditions are described in which extracts of m13-infected e. coli and membranes prepared from such extracts will support virus assembly at a rate equivalent to that of intact cells. extracts prepared from cells infected with temperature-sensitive m13 mutants in genes 1, 3 ... | 1977 | 15248 |
| high-resolution 31p nuclear magnetic resonance studies of metabolism in aerobic escherichia coli cells. | 31p nuclear magnetic resonance spectra at 145.7 mhz were obtained of concentrated suspensions of e. coli cells. the position of the pi resonance was used to determine the ph, and in most experiments it was possible to distinguish the intracellular (phin) and extracellular (phex) values. during respiration phin approached 7.55, while phex varied from 6.0 to 8.0. with succinate as a carbon source and in a n2 environment, phin - phex. upon addition of glucose, phin greater than phex. in the presenc ... | 1977 | 15257 |
| the effect escherichia coli lipopolysaccharide (endotoxin) on the graft-versus-host reaction in mice (iv). | lipopolysaccharide from escherichia coli (lps) administered to mice during the graft-versus-host (gvh) reaction in a single dose of 100 mug stimulated the reaction if it was given on the same day as the parental spleen cells, or inhibited it if given four days before injection of the cells. the gvh reaction was intensified when lps was injected in the dose of 20 mug on the fourth day after injection of the cells. the parental spleen cells responsible for the intestifying effect on gvh were sensi ... | 1976 | 15368 |
| study of penicillin amidase from e. coli. ph-dependence of kinetic parameters of enzymatic hydrolysis of benzylpenicillin. | the authors studies ph-dependencies of the kinetic parameters (vm, km, vm/km) and constants of competitive inhibition by phenylacetic acid of penicillinamidase-catalyzed hydrolysis of benzylpenicillin. the experimental data are in agreement with the assumption according to which there are 3 equilibrium ionogenic forms of the enzyme and enzyme-substrate (or enzyme-inhibitor) complexes, i.e. acidic, neutral and alkaline, the neutral form being the only active form of the michaelis complex. values ... | 1976 | 15503 |
| penicillin amidase from e. coli. a direct spectrophotometric method of determining the enzyme's activity. | a method for determination of the enzymatic activity of penicillinamidas (pa) based on spectrophotometric estimation of the stained product amount produced in hydrolysis of 4-phenylacetamido-2-nitrobenzoic acid (panba) catalyzed by the enzyme is proposed. some physico-chemical properties of the substrate and the stained product were studied. the kinetic parameters of the panaba enzymatic hydrolysis were determined. catalytic activity of some enzyme products of pa of different purity levels was s ... | 1977 | 15505 |
| effect of culture conditions on synthesis of l-asparaginase by escherichia coli a-1. | the nutritional requirements and culture conditions affecting biosynthesis of l-asparaginase in a mutant of escherichia coli hap designated strain a-1 were studied. asparaginase activity was increased by the addition of l-glutamic acid, l-glutamine, or commercial-grade monosodium glutamate. the rate of enzyme synthesis was dependent on the interaction between the ph of the culture and the amount of oxygen dissolved in the medium. a critical oxygen transfer rate essential for asparaginase format ... | 1977 | 15509 |
| proton uptake linked to the 3-deoxy-2-oxo-d-gluconate-transport system of escherichia coli. | genetic and kinetic evidence is presented to show that the carrier-mediated uptake of the anionic sugars 3-deoxy-2-oxo-d-gluconate and d-glucuronate by escherichia coli involves the concomitant transport of protons. | 1977 | 15555 |
| transport of galactose, glucose and their molecular analogues by escherichia coli k12. | 1. strains of escherichia coli k12 were made that are unable to assimilate glucose by the phosphotransferase system, since they lack the glucose-specific components specified by the genes ptsg and ptsm. 2. derivative organisms lacking the methyl galactoside or galactose-specific transport system were examined for their ability to transport galactose, d-fucose, methyl beta-d-galactoside, glucose, 2-deoxy-d-glucose and methyl alpha-d-glucoside. 3. galactose, glucose and to a lesser extent fucose a ... | 1977 | 15558 |
| determination of metal-metal distances in e. coli glutamine synthetase by epr. | | 1977 | 15566 |
| comparison of the biosynthetic and biodegradative ornithine decarboxylases of escherichia coli. | biosynthetic ornithine decarboxylase was purified 4300-fold from escherichia coli to a purity of approximately 85% as judged by polyacrylamide gel electrophoresis. the enzyme showed hyperbolic kinetics with a km of 5.6 mm for ornithine and 1.0 micronm for pyridoxal phosphate and it was competitively inhibited by putrescine and spermidine. the biosynthetic decarboxylase was compared with the biodegradative ornithine decarboxylase applebaum, d., et al. (1975), biochemistry 14, 3675. both enzymes w ... | 1977 | 15587 |
| purification and crystallization of nadp+-specific isocitrate dehydrogenase from escherichia coli using polyethylene glycol. | a simple and rapid method is presented for purifying the nadp+-dependent isocitrate dehydrogenase (threo-ds-isocitrate:nadp+ oxidoreductase (decarboxylating), from escherichia coli, which relies on fractionation of the enzyme with polyethylene glycol. the shortened preparation results in a 32% relative recovery of purified enzyme at a specific activity of 127 micronmol/min per mg of protein. the km values for threo-ds-isocitrate, nadp+, nad+, mg2+ and mn2+ are 6.4, 36, 3000, 19.7 and 2.0 micronm ... | 1977 | 15602 |
| selective reactions of nucleobases under biological conditions. | pentacyanonitrosylferrate/ii/ complex reacts under biological conditions (ph= 7.5, t= 25-40 degrees c, dilute solution) selectively with nucleobases. the reaction with adenine and guanine probably leads to nitrosation. a new compound formed in the reaction with adenine is prepared; both this compound and the pentacyanonitrosylferrate/ii/ inhibits the multiplication of escherichia coli. | 1977 | 15627 |
| o-demethylation of p-nitroanisole by escherichia coli. stimulation by phenobarbital. | intact cells of the bacterium escherichia coli atcc 11229, can convert p-nitroanisole into p-nitrophenol. the presence of phenobarbital in the culture medium during growth of the cells results in an inhibition of bacterial cell mass and an increased ability of the bacterial cell to carry out the o-demethylation reaction. there was a linear relationship between the amount of product formed and the bacterial cell mass in the incubation mixture. varying the substrate concentration gave a concomitan ... | 1977 | 15812 |
| study of the conditions for concentrating the poliomyelitis virus and e. coli bacteriophages on ion-exchange resins. | | 1977 | 15925 |
| nutrition and enterotoxin synthesis by enterotoxigenic strains of escherichia coli: defined medium for production of heat-stable enterotoxin. | a defined medium has been developed which supports synthesis of heat-stable enterotoxin (st) by porcine and bovine strains of enterotoxigenic (ent+) escherichia coli in levels equivalent or better than a complex casamino acids-salts medium. the medium components did not support production of heat-labile enterotoxin (lt) but were similar for st synthesis by ent+ strains producting only st and those which produced st in addition to lt. the amino acids in casamino acids found to be necessary for gr ... | 1977 | 15947 |
| cell envelope protection of alkaline phosphatase against acid denaturation in escherichia coli. | the effects of a highly acidic environment on the cell-associated alkaline phosphatase activities of a smooth and a rough strain of escherichia coli o8 have been examined. the observation that cell-associated enzyme is denatured to a lesser degree than purified enzyme suggests that the association of the enzyme with the cell envelope affords it some degree of protection from potentially disruptive agents in the environment. the degree of protection afforded the enzyme from ph denaturation appear ... | 1977 | 15981 |
| escherichia coli mutants deficient in the aspartate and aromatic amino acid aminotransferases. | two new mutations are described which, together, eliminate essentially all the aminotransferase activity required for de novo biosynthesis of tyrosine, phenylalanine, and aspartic acid in a k-12 strain of escherichia coli. one mutation, designated tyrb, lies at about 80 min on the e. coli map and inactivates the "tyrosine-repressible" tyrosine/phenylalanine aminotransferase. the second mutation, aspc, maps at about 20 min and inactivates a nonrespressible aspartate aminotransferase that also has ... | 1977 | 15983 |
| endonuclease from escherichia coli that acts specifically upon duplex dna damaged by ultraviolet light, osmium tetroxide, acid, or x-rays. | an endonuclease which is active upon dna exposed to ultraviolet light at a photoproduct other than thymine dimers has been extensively purified from escherichia coli. the small (2.7 s) enzyme is active in the presence of edta, has a neutral ph optimum, and is inhibited by trna and 1 m nacl. it has no detectable exonuclease, dna-n-glycosidase, or ribonuclease activities. the enzyme also nicks duplex dna exposed to oso4, x-rays, or acid, but it does not act upon undamaged dna or irradiated single- ... | 1977 | 16001 |
| a new endonuclease from escherichia coli acting at apurinic sites in dna. | a new dna endonuclease has been purified 3000-fold from escherichia coli. the enzyme specifically catalyzes the formation of single strand breaks at apurinic and apyrimidinic sites in dna, but has no activity on intact or single-stranded dna. further, the enzyme shows little or no activity on heavily ultraviolet-irradiated dna, but cleaves x-irradiated dna, presumably at apurinic and apyrimidinic sites introduced by the radiation treatment. the enzyme, which is tentatively named endonuclease iv, ... | 1977 | 16002 |
| lack of a regulatory function for glutamine synthetase protein in the synthesis of glutamate dehydrogenase and nitrite reductase in escherichia coli k12. | synthesis of glutamine synthetase (gs) in anaerobic batch cultures of escherichia coli was repressed when excess nh4+ was available, but derepressed during growth with a poor nitrogen source. in wild-type bacteria there was only a weak inverse correlation between the activities of gs and glutamate dehydrogenase (gdh) during growth in various media. no positive correlations were found between the activities of gs and nitrite reductase, or between gs and cytochrome c552: both of these proteins wer ... | 1977 | 16079 |
| evaluation of the role of methional, 2-keto-4-methylthiobutyric acid and peroxidase in ethylene formation by escherichia coli. | during growth of escherichia coli strain spa o in the presence of methionine, an intermediate accumulates in the medium. this intermediate reacts with 2,4-dinitrophenylhydrazine, and can be degraded to ethylene either enzymically or photochemically, the latter being stimulated by the addition of a flavin. the ph optimum for the photochemical degradation of this intermediate and 2-keto-4-methylthiobutyric acid (kmba) is ph 3 whereas the optimum for methional is ph 6. the enzyme which converts the ... | 1977 | 16080 |
| the product of a newly identified gene, ginf, is required for synthesis of glutamine synthetase in salmonella. | the product of a newly identified gene, glnf, which is distinct from the glutamine synthetase structural gene (glna), is required for synthesis of glutamine synthetase l-glutamate:ammonia ligase (adp-forming), ec 6.3.1.2 in salmonella typhimurium and probably in escherichia coli. salmonella strains with icr (2-chloro-6-methoxy-9-3-(2-chloroethyl)aminopropylaminoacridine dihyodrochloride)-induced (frameshift) mutations in glnf are glutamine auxotrophs; they have less than 10% oof wild-type glutam ... | 1977 | 16262 |
| penicillin amidase from e. coli. some physicochemical properties of the soluble enzyme. | homogeneity of the enzyme was shown with the methods of gel filtration and disc electrophoresis. the molecular mass of penicillinamidase (pa) was determined. sorption of pa by a carboxylic ion exchanger within a wide range of ph was studied. the values of ph in the ion exchanger phase under the conditions of the enzyme sorption were estimated. the ion exchange technique for determination of the isoelectric points of the proteins is described and the isoelectric point of pa is determined. it is p ... | 1977 | 16562 |
| penicillin amidase from e. coli. some physicochemical properties of the enzyme incorporated into polyacrylamide gel. | the physico-chemical properties of penicillinamidase (pa) immobilized in polyacrylamide gel (ipa) were investigated. it was shown that simple incorporation of pa into polyacrylamide gel was not effective because of gradual washing out of the enzyme. the use of a complex method for the immobilization (immobilization in the presence of a linking agent) resulted in higher stability of ipa, the choice of the optimal ratio of the reagents being of paramount importance. the mechanical strength of ipa ... | 1977 | 16563 |
| methylammonium uptake by escherichia coli: evidence for a bacterial nh4+ transport system. | | 1977 | 16600 |
| proton nuclear magnetic resonance study of the effect of ph on trna structure. | the low-field 220-mhz proton nuclear magnetic resonance (nmr) spectra of four trna molecules, escherichia coli trnaphe, trna1val, and trnafmet1, and yeast trnaphe, at neutral and mildly acidic ph are compared. we find a net increase in the number of resonances contributing to the -9.9-ppm peak (downfield from sodium 4,4-dimethyl-4-silapentanesulfonate) in three of these trnas at ph 6, while trnafmet1 does not clearly exhibit this behavior. the increase in intensity at this resonance position is ... | 1977 | 16638 |
| specific phospholipid requirement for activity of the purified respiratory chain nadh dehydrogenase of escherichia coli. | the highly purified respiratory chain nadh dehydrogenase (ec 1.6.99.3) of escherichia coli is inactive in the absence of detergent or phospholipid. triton x-100 is the detergent that gives optimal activity, but the triton x-100-activated enzyme is stimulated an additional 2-fold by e. coli phospholipids. phosphatidylglycerol and diphosphatidylglycerol are the most effective lipid activators. the activated complex prepared with diphosphatidylglycerol is stable, whereas that with phosphatidylglyce ... | 1977 | 16660 |
| uridine phosphorylase from escherichia coli. physical and chemical characterization. | uridine phosphorylase from escherichia coli has been purified to homogeneity. the enzyme was found to have a molecular weight of 176000 and to consist of 8 probably identical subunits with molecular weights of 22000. these numbers were determined from equilibrium centrifugations in the analytical ultracentrifuge, from dodecylsulphate gel electrophoresis and from amino acid analysis. moreover the following physico-chemical constants were determined: s020,w = 8.2 x 10(-13) s, upsilon2 = 0.751 cm3/ ... | 1977 | 16751 |
| regulation of enzyme synthesis by the glutamine synthetase of salmonella typhimurium: a factor in addition to glutamine synthetase is required for activation of enzyme formation. | in klebsiella aerogenes but not in salmonella typhimurium glutamine synthetase can function during nitrogen-limited growth to increase the rate of synthesis of histidase from the hut genes of s. typhimurium 15-59 (huts. 15-59). formation of proline oxidase is also not increased in nitrogen-limited cultures of s. typhimurium. however, in hybrid strains of escherichia coli or k. aerogenes, the glutamine synthetase of s. typhimurium activates synthesis of histidase from the huts. 15-59 genes. appar ... | 1977 | 16868 |
| phosphoenolypyruvate synthetase of escherichia coli: molecular weight, subunit composition, and identification of phosphohistidine in phosphoenzyme intermediate. | phosphoenolypyruvate synthetase of escherichia coli has been shown to be a dimer of molecular weight 150,000. the constituent subunits appear to be identical. the enzyme tends to dissociate to monomers at low protein concentration, but the tendency is much diminished in the phosphoenzyme form, suggesting that enzyme phosphorylation is accompanied by a structural rearrangement in the subunit contact domain. the enzyme appears to show half of the sites reactivity with respect to its phosphorylatio ... | 1977 | 16880 |
| isolation of glutamic acid methyl ester from an escherichia coli membrane protein involved in chemotaxis. | we have isolated glutamic acid 5-methyl ester from an escherichia coli protein that is involved in chemotaxis. the bacteria were first incubated with methyl-3hmethionine under conditions which are known to result in methylation of the protein. the protein, isolated by gel electrophoresis, was then digested by successive treatment with three proteolytic enzymes. one of the products was methyl-3hglutamic acid 5-methyl ester, identified by comparison with an authentic sample in the following studie ... | 1977 | 16888 |
| n-acetylglutamate synthase of escherichia coli: purification, characterization, and molecular properties. | | 1977 | 16890 |
| pathways of nadph formation in escherichia coli. | | 1977 | 16899 |
| characterization of escherichia coli mutant incapable of maintaining a transmembrane potential. metc ecfts mutations. | | 1977 | 16923 |
| charges of nicotinamide adenine nucleotides and adenylate energy charge as regulatory parameters of the metabolism in escherichia coli. | methods for measurements of catabolic reduction charge (defined as nadh/(nadh+nad+)) and anabolic reduction charge (defined as nadph/(nadph + nadp+)) are described using 14cnicotinamide labeling of escherichia coli cultures. together with these parameters the adenylate energy charge (atp + 1/2adp)/(atp + adp + amp) was measured using labeling with 2-3hadenine. these three charges were found under different exponential growth conditions to have values independent of the growth conditions: catabol ... | 1977 | 16925 |
| phosphoprotein phosphatase activity associated with the cytoplasmic membrane of salmonella typhimurium and escherichia coli. | membrane-associated phosphoprotein phosphatase activity was demonstrated in extracts of salmonella typhimurium and escherichia coli. the active protein could be extracted from the membrane as a large water-soluble complex (mr greater than 150,000). maximal activity was observed at ph 6 to 7 in the presence of a divalent cation. the enzyme appears to be distinct from previously described phosphatases. | 1977 | 16933 |
| nosocomial bacteremia. potential for prevention of procedure-related cases. | during a six-month period, 187 inpatients had bacteremia associated with community-acquired infection and 91 patients had bacteremia from a nosocomial infection. the most frequently identified sites of infection in both types of bacteremia were the respiratory and urinary tracts. escherichia coli and diplococcus pneumoniae were the organisms most frequently isolated from cultures of patients with community-acquired bacteremia, and e coli, staphylococcus aureus, and klebsiella were most frequentl ... | 1977 | 17018 |
| in vitro examination on antibacterial activity of ciclacillin (acpc) against clinically isolated strains (author's transl). | (1) the antibacterial acivity of ciclacillin (acpc) with inoculum size of 10(6) cells/ml was four times less potent than that of ampicillin (abpc) and 4 approximately 8 times less potent than that of ampc, but was 4 approximately 8 times more potent than that of cex against streptococcus pyogenes. for streptococcus pneumoniae, acpc was 2 approximately 4 times less active than abpc and ampc, but 16 approximately 32 times more active than cex. staphylococcus aureus was 4 approximately 8 times less ... | 1977 | 17021 |
| aminoacylation of trna trp from beef liver, yeast and e. coli by beef pancrease tryptophan-trna ligase. stoichiometry of trnatrp binding. | the michaelis constants and the maximum velocities in the aminoacylation reaction of trnatrp from beef liver, yeast and e. coli by pure beef pancreas tryptophan-trna ligase show that this mammalian enzyme recognizes and charges the two eucaryotic trnas with the same efficiency. the rate of aminoacylation of the procaryotic trnatrp by the enzyme is three orders of magnitude lower. the ph optimum of aminoacylation is 8 for both eucaryotic trnas. the optimum magnesium concentration is different. th ... | 1977 | 17096 |
| purification and properties of l-asparaginase ec-2 from escherichia coli 055:b5. | 1. l-asparaginase has been isolated from aerobically grown escherichia coli 055:b5 and purified about 140-fold in a three-step procedure involving acidification to ph 4.5, ammonium sulphate fractionation and column chromatography on deae-sephadex a-50. the activity of the preparation is 140 u/mg protein. 2. the enzyme acts within a broad ph range (ph 5-9) and is affected neither by pcmb, n-ethylmaleimide nor metal ions. 3. molecular weight of the isolated asparaginase is 130 000. | 1977 | 17256 |
| occurrence in mammalian liver of a protein which replaces the b protein of e. coli quinolinate synthetase. | | 1977 | 17402 |
| co-transport of na+ and methul-beta-d-thiogalactopyranoside mediated by the melibiose transport system of escherichia coli. | | 1977 | 17404 |
| purification and properties of trna(adenine-1)-methyltransferase from rat liver. | an s-adenosylmethionine-dependent trna(adenine-1)-methyltransferase has been purified 8,000-fold from rat liver. this preparation gives a single band on polyacrylamide gel electrophoresis and is stable in long term storage. the enzyme has a molecular weight of approximately 95,000. the single methylating capacity of this adenine-1 methyltransferase, using escherichia coli trna2glu, is methylation of the invariant adenine in the gtpsic loop. the methylation reaction is dependent on added cation w ... | 1977 | 17605 |
| bistability in the activity of glutamine synthetase in ammonium-limiting chemostat cultures of escherichia coli ml 30. | the approximative estimation of the function micron(nh+4) in cultures of e. coli ml 30 had shown that bistability of the ammonium concentration in ammonium limited continuous cultures could be possible (bergter et al. 1977). this phenomenon suggested a bistability in the regulation of ammonia assimilation. therefore, the activity of one key enzyme of the two ammonia assimilation systems was measured. the distribution of the activity of glutamine synthetase in ammonia limited continuous cultures ... | 1977 | 17951 |
| azlocillin: in vitro studies of a new semisynthetic penicillin. | the activity of azlocillin, a new semisynthetic penicillin, was determined against 582 clinical isolates of gram-negative bacilli and gram-positive cocci. over 75% of the isolates of pseudomonas aeruginosa were inhibited at a concentration of 12.5 mug or less per ml. azlocillin is also active against indole-negative and -positive proteus spp., inhibiting 98 and 71%, respectively, at a concentration of 12.5 mug or less per ml. isolates of klebsiella spp. and enterobacter spp. showed less suscepti ... | 1977 | 18083 |
| significance of fecal coliform-positive klebsiella. | a total of 191 klebsiella pneumoniae isolates of human clinical, bovine mastitis, and a wide variety of environmental sources were tested for fecal coliform (fc) response with the membrane filtration and most probable number techniques. twenty-seven escherichia coli cultures of human clinical and environmental origins were also tested. eighty-five percent (49/58) of known pathogenic k. pneumoniae were fc positive, compared with 16% (19/120) of the environmental strains. e. coli results indicated ... | 1977 | 18086 |
| steady state kinetic mechanism of the escherichia coli coenzyme a transferase. | | 1977 | 18103 |
| proton translocation coupled to electron flow from endogenous substrates to fumarate in anaerobically grown escherichia coli k12. | observed leads to h+/2e- values for proton translocation during the reduction of fumarate by endogenous substrates in anaerobic cells of escherichia coli k12 varied with fumarate concentration. this variation was probably due mainly to incomplete fumarate utilization. under optimum conditions a minimum value for leads to h+/2e- of 1.04+/-0.20 was obtained. | 1977 | 18144 |
| extrinsic and intrinsic factors that influence inactivation and purification of the unstable adenosine triphosphatase solubilized from membranes of an escherichia coli k 12 strain. | | 1977 | 18189 |
| binding of alkyl 1-thio-beta-d-galactopyranosides to beta-d-galactosidase from e. coli. | the binding of a series of alkyl 1-thio-beta-d-galactopyranosides to beta-d-galactosidase from e. coli has been investigated. the inhibition constants were compared to the partition coefficients for the transfer of these substrate-analogues from water to 1-octanol. the relationships between the observed binding-constants and the partition coefficients indicate that part of the aglycon group binds to a hydrophobic area that is limited in relation to the length of hydrocarbon chain that can be acc ... | 1977 | 18283 |