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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Flagellin, the protomeric subunit of bacterial flagella, contains no cysteine. We have detected the incorporation of trace quantities of 35S-cysteine into flagellin, highly purified and then resolved by SDS polyacrylamide gel electrophoresis, to measure mistranslation in vivo. Under normal conditions, this value is about 6 X 10(-4) pmoles cysteine per pmole flagellin. This value is greatly increased during growth in low concentrations of streptomycin and neomycin, antibiotics which are known to stimulate misreading in vitro. Of the specific types of misreading which streptomycin stimulates in vitro, only misreading of the CGU and CGC arginine codons could give rise to illegitimate incorporation of cysteine. In agreement, partial arginine starvation increases the incorporation of 35S-cysteine into flagellin in a relA- mutant, with or without streptomycin, but has no such effect in its isogenic relA+ partner- Assuming from these results that 35S-cysteine incorporation into flagellin reflects misreading of CGU/C coda, we deduce a misreading probability per codon in the range of 10(-4).
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PMID:Mistranslation in E. coli. 13 85

The rate of synthesis of ribosomal proteins relative to that of total protein was measured at various times during recovery from arginine starvation in isogenic re+ and rel- strains of Escherichia coli K 12. Total ribosomal proteins are preferentially synthesized early during recovery. Higher rates of synthesis are obtained in the rel+ strain than in the rel- strain. Differential rates of synthesis of individual ribosomal proteins are observed at the various times studied. The rate of synthesis of individual proteins increases with time up to maximum values then the rates come down to values similar to those found in exponentially growing cells. The time of restart of synthesis of each protein has been estimated (1) by the time at which the maximum value is reached, and (2) by measuring the rate of synthesis at early time (3 min). Most ribosomal proteins behave similarlly in rel- and rel+ strains. Proteins have been listed from highly labelled (early proteins) to poorly labelled (late proteins). The significance of the order of restart is considered.
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PMID:On the control of ribosomal protein biosynthesis in Escherichia coli. II. Studies during recovery from amino acid starvation. 32 Oct 27

The content of myosin in plasmodia of the myxomycete Physarum polycephalum was measured by an immunological technique, quantitative microcomplement (C') fixation. Migrating plasmodia (starved after growth on rolled oats) contained 0.60 +/- 0.08 (SD) mg myosin per g fresh plasmodia. Myosin comprised 0.77% +/- 0.05 (SD) of the total plasmodial protein. When total plasmodial proteins were separated by electrophoresis on SDS-polyacrylamide gels, a large amount of protein appeared in a band comigrating with muscle actin. Densitometry performed after Coomassie blue staining indicated that as much as 15-25% of the total protein in the plasmodium could be actin. This gives an actin/myosin ratio by weight in the myxomycete plasmodium as high as 19-33, a very "actin-rich" actomyosin compared with rabbit skeletal muscle actomyosin with an actin/myosin ratio of 0.6. Starvation stimulates rapid migration and is correlated with a higher percent of both myosin and actin in the total protein of the plasmodium compared with normally growing cultures. Immunological cross-reaction of myosins from a variety of species was measured by C' fixation using an antiserum produced against purified native myosin from P. polycephalum. Although myxomycete and vertebrate striated muscle myosins have very similar morphological and biochemical properties, and apparently possess similar binding properties to F-actin, only myosins from myxomycetes in the order Physarales, rather closely related to P. polycephalum, gave detectable cross-reactions. This finding suggests that many amino acid sequences in myosin have been variable during evolution.
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PMID:Actomyosin content of Physarum plasmodia and detection of immunological cross-reactions with myosins from related species. 94 88

We previously found a trypsin-like proteinase which momentarily appears immediately before DNA synthesis in the cell cycle of Escherichia coli synchronized by phosphate starvation and which is closely related to the initiation of DNA replication (Kato, M., Irisawa, T., Morimoto, Y. and Muramatu, M., unpublished results). The proteinase was named proteinase In. It was purified approximately 2880-fold with a recovery of 15%. The isolated enzyme appeared homogeneous by gel filtration and electrophoresis. Its molecular mass was estimated by analytical gel filtration and SDS/PAGE as approximately 66 kDa. The isoelectric point of proteinase In is 4.9 and its optimal pH is approximately 9. Although protein In hydrolyzes fluorogenic substrate for trypsin, its hydrolytic activity seems markedly affected by amino-acid sequence lying towards the N-terminal from the P1 (lysine, arginine) residue. The proteinase does not hydrolyze N2-benzoyl-D,L-arginine-4-nitronanilide and fluorogenic substrates for chymotrypsin and elastase. The proteinase activity is inhibited by leupeptin, antipain and 4-nitrophenyl 4-guanidinobenzoate, but the effects of tosyl-L-lysine chloromethane, diisopropylfluorophosphate, benzamidine and pentamidine isethionate on the proteinase activity are weak or not inhibitory. Its activity is strongly affected in the presence of NaCl and KCl, and at a concentration of 1.5 M, these increase the activity 14-fold and 13-fold, respectively, above that without salt. Proteinase In was strongly inhibited by various esters of trans-4-guanidinomethylcyclohexanecarboxylic acid, and their inhibitory effects were roughly correlated with those on growth of E. coli. Proteinase activity was found in the cytoplasmic fraction.
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PMID:Purification and characterization of proteinase In, a trypsin-like proteinase, in Escherichia coli. 133 54

The isoform of cytochrome P450 that catalyzes the 12 alpha-hydroxylation of 7 alpha-hydroxy-4-cholesten-3-one, an intermediate in the conversion of cholesterol to cholic acid, was purified to homogeneity from rabbit liver microsomes. The extent of purification in the various steps was judged by an assay involving high performance liquid chromatography. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis (M(r) = 50,000). The NH2-terminal amino acid sequence is as follows: Val-Leu-Trp-Gly-Leu-Leu-Gly-Ala-Leu-Leu-Met-Val-Met-Val-Gly-, which is different from that of any other P450s so far reported. The specific content of the enzyme was 13.3 nmol of cytochrome P450/mg of protein. Upon reconstitution with NADPH-cytochrome P450 reductase and cytochrome b5, the P450 enzyme showed a high activity of 12 alpha-hydroxylation with a turnover number of 36.6 min-1 at 37 degrees C. The omission of either cytochrome P450 or NADPH-cytochrome P450 reductase resulted in complete loss of activity, and the omission of cytochrome b5 resulted in 40% loss of activity. Antibodies prepared from mouse inhibited the 12 alpha-hydroxylase activity of rabbit liver microsomes about 90% and that of the rat liver microsomes 50%. The enzyme activity was not inhibited by other antibodies raised against other forms of P450 that catalyze different monooxygenation reactions toward xenobiotics or endogenous substrates. Anti-cytochrome b5 antibody inhibited the activity 40%, suggesting the functional role of this protein, and anti-reductase inhibited the activity almost completely. The microsomal enzyme activity was markedly elevated by starvation or streptozotocin administration to the animals. However, an immunoblotting experiment showed no correlation between the enzyme activity and the amount of protein, suggesting that post-translational modification may occur.
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PMID:Purification and characterization of 7 alpha-hydroxy-4-cholesten-3-one 12 alpha-hydroxylase. 140 Apr 44

The Candida albicans PMA1 gene was isolated from a genomic library by using a hybridization probe obtained from the PMA1 gene of Saccharomyces cerevisiae. The gene was localized to chromosome III of the Candida genome. An open reading frame of 2,685 nucleotides predicts an amino acid sequence of 895 amino acids that is 83% homologous at both the DNA and protein levels to its S. cerevisiae equivalent. A polyadenylated mRNA transcript of about 4,000 nucleotides contains a highly folded AU-rich leader of 242 nucleotides. The structure of the gene, codon bias, and levels of approximately 100-kDa H(+)-ATPase protein recovered in plasma membranes indicate a highly expressed gene. The plasma membrane ATPase was purified to about 90% homogeneity and appeared to be blocked at the amino terminus. Three hydrophobic membrane sector tryptic fragments from the partially digested ATPase provided internal sequence information for over 50 amino acids, which agrees with the sequence predicted by the cloned gene. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the C. albicans enzyme is about 3 kDa smaller than its Saccharomyces counterpart and was consistent with a predicted Mr of 97,398. Antibodies to the S. cerevisiae whole ATPase or its carboxyl terminus bound to the C. albicans enzyme but with lower avidity. Kinetic analysis showed that the Candida and Saccharomyces ATPases respond to glucose activation-starvation in nonidentical fashions. The amino-terminal domain of the C. albicans ATPase is marked by a net deletion of 23 amino acids in comparison with the S. cerevisiae ATPase. These differences maintain net charge, occur in nonconserved regions of fungal ATPases, and are sufficient to account for the observed difference in electrophoretic mobility between the two yeast ATPases.
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PMID:Cloning and characterization of the plasma membrane H(+)-ATPase from Candida albicans. 183 33

Cysteine proteinase activities have been determined using gelatin-SDS-PAGE analysis and assays based on peptide nitroanilides. Vegetative myxamoebae of all species examined contain high levels of cysteine proteinase activity present in multiple forms. In both Dictyostelium discoideum and Polysphondylium pallidum the proteinase content is dependent on whether the cells are grown axenically or in association with bacteria. In all instances development is accompanied by a decreased intracellular cysteine proteinase activity. This occurs during the formation of fruiting bodies in D. discoideum, microcysts in P. pallidum, and macrocysts in Dictyostelium mucoroides. Significant quantities of proteinase activity are always secreted by myxamoebae immediately on starvation. In D. mucoroides this leads to an almost total depletion of intracellular cysteine proteinases by the aggregation stage. As a consequence of this depletion it has been relatively easy to detect a developmentally regulated accumulation of cysteine proteinases at the enzyme activity level, something which has not yet proved possible with D. discoideum. Three cysteine proteinases are produced as D. mucoroides macrocysts develop and mature. In the case of microcyst formation in P. pallidum the proteinase contents of the developing cells and of the microcysts are dependent on how the myxamoebae are grown. In this developmental pathway at least, there is no absolute requirement for specific proteinases to be present (or absent) at a particular stage. The diversity of cysteine proteinases found in cellular slime molds and the variety of features apparent in their regulation suggest that they will prove to be very useful for investigating features of the structure/function relationships in this important group of enzymes.
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PMID:Regulation of cysteine proteinases during different pathways of differentiation in cellular slime molds. 204 75

Wild-type Neurospora crassa grown in minimal medium was exposed to -difluormethyl ornithine (DFMO), a specific inhibitor of ornithine-decarboxylase (ODC-ase) activity. Protein-synthesis rates impaired by DFMO were restored by the addition of spermidine. The pattern on SDS-acrylamide gels displayed three newly synthesized polypeptides, p27, p31 and p99 after DFMO action in the absence of exogenous polyamine. The ODC-ase mutant (spe-1) grown in spermidine-supplemented medium did not show an induced polypeptide pattern. The lack of ODC-ase activity promotes the expression of p27- and p31-coding genes in both strains but transcription of p31 gene is shut-off after spermidine addition. Both transcripts are also accumulated after exposure to low cycloheximide doses or nutrient starvation. Another cycloheximide-inducible gene coding for p70 is also expressed under DFMO-treatment.
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PMID:Genes responsive to the alteration of polyamine biosynthesis in neurospora crassa. 213 6

It has been shown previously that starvation of the trypanosomatid protozoan Crithidia luciliae for purines and/or inorganic phosphate results in increased levels of a surface membrane-associated 3'-nucleotidase/nuclease (3'-N'ase) activity which hydrolyzes both 3'-ribonucleotides and nucleic acids, thereby permitting the organisms to transport these essential nutrients across their cell membranes. A polypeptide with the requisite catalytic properties has been identified by an in situ gel activity assay following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In current studies, differential synthesis of the protein responsible for the 3'-N'ase activity was not demonstrable by comparisons of SDS-PAGE patterns of nutrient-replete or purine-starved parasites metabolically labeled with either [35S]methionine, [3H]leucine, or [3H]tyrosine. However, surface labeling of nutrient-replete and purine-starved cells revealed the enhanced expression of an 125I surface-labeled 43-kDa protein which comigrated with the 3'-N'ase activity in one- and two-dimensional electrophoretic systems. The amount of this surface-labeled peptide correlated with the level of 3'-N'ase activity as measured by test tube assay. Refeeding adenosine to purine-starved cells led to the loss of both the enzyme activity and the surface iodinatable 43-kDa band as a result of renewed cell division. Starvation of these organisms for phosphate also led to the enhanced expression of the 43-kDa radioiodinatable band. The results indicated that the 3'-N'ase protein, itself, is differentially expressed at the cell surface under conditions which lead to increased enzyme activity.
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PMID:Crithidia luciliae: starvation for purines and/or phosphate leads to the enhanced surface expression of a protein responsible for 3'-nucleotidase/nuclease activity. 216 51

Pseudomonas aeruginosa PAO1 was grown in vivo in chambers implanted into the peritoneums of mice and rats. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extracts of bacterial cells taken from the chambers and washed to remove loosely bound host proteins revealed the presence of the major outer membrane proteins D2, E, F, G, and H2. Western immunoblotting with specific antisera confirmed the presence of porin protein F and lipoprotein H2. However, there was no apparent induction of the phosphate starvation-inducible porin P or the divalent cation starvation-inducible protein H1. Small amounts of proteins with molecular weights similar to those of the iron-regulated outer membrane proteins were found in cells grown in vivo; however, their presence could not be confirmed immunologically. The presence of pili and flagella on the cells grown in vivo was demonstrated by electron microscopy and Western immunoblotting. A consistent alteration in the lipopolysaccharide banding pattern was observed after growth in vivo. Compared with cells of strain PAO1 grown in vitro, cells grown in vivo appeared to lack a series of high-molecular-weight O-antigen-containing lipopolysaccharide bands and gained a new series of lower-molecular-weight lipopolysaccharide bands. This alteration in the lipopolysaccharide after growth in vivo did not affect the O-antigen serotype or the resistance of the bacteria to serum.
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PMID:Surface characteristics of Pseudomonas aeruginosa grown in a chamber implant model in mice and rats. 249 57


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