RESUMO
Most organisms grow at temperatures from 20 to 50 degrees C, but some prokaryotes, including Archaea and Bacteria, are capable of withstanding higher temperatures, from 60 to >100 degrees C. Their biomolecules, especially proteins, must be sufficiently stable to function under these extreme conditions; however, the basis for thermostability remains elusive. We investigated the preferential usage of certain groupings of amino acids and codons in thermally adapted organisms, by comparative proteome analysis, using 28 complete genomes from 18 mesophiles (M), 4 thermophiles (T), and 6 hyperthermophiles (HT). Whenever the percent of glutamate (E) and lysine (K) increased in the HT proteomes, the percent of glutamine (Q) and histidine (H) decreased, so that the E + K/Q + H ratio was >4.5; it was <2.5 in the M proteomes, and 3.2 to 4.6 in T. The E + K/Q + H ratios for chaperonins, potentially thermostable proteins, were higher than their proteome ratios, whereas for DNA ligases, which are not necessarily thermostable, they followed the proteome ratios. Analysis of codon usage revealed that HT had more AGR codons for Arg than they did CGN codons, which were more common in mesophiles. The E + K/Q + H ratio may provide a useful marker for distinguishing HT, T and M prokaryotes, and the high percentage of the amino acid couple E + K, consistently associated with a low percentage of the pair Q + H, could contribute to protein thermostability. The preponderance of AGR codons for Arg is a signature of all HT so far analyzed. The E + K/Q + H ratio and the codon bias for Arg are apparently not related to phylogeny. HT members of the Bacteria show the same values as the HT members of the Archaea; the values for T organisms are related to their lifestyle (intermediate temperature) and not to their domain (Archaea) and the values for M are similar in Eukarya, Bacteria and Archaea
Assuntos
Aminoácidos/genética , Archaea/crescimento & desenvolvimento , Bactérias/crescimento & desenvolvimento , Temperatura Alta , Adaptação Biológica , Archaea/química , Archaea/genética , Bactérias/química , Bactérias/genética , DNA Ligases/análise , DNA Ligases/genética , Proteínas de Bactérias/genética , Proteoma/análise , Proteoma/genéticaRESUMO
Changes in phosphorylation of ribosomal protein S6 during heat shock, induction of thermotolerance and recovery from heat shock at different stages of Blastocladiella emersonii development were investigated. Independently of the initial state of S6 phosphorylation (maximal or intermediate), a rapid and complete dephosphorylation of S6 is induced by heat shock and S6 remains unphosphorylated during the acquired thermotolerance. During recovery from heat shock rephosphorylation of S6 occurs always to the levels characteristic of that particular stage, coincidently with the turn off of heat shock protein synthesis.
Assuntos
Blastocladiella/metabolismo , Quitridiomicetos/metabolismo , Proteínas de Choque Térmico/metabolismo , Proteínas Ribossômicas/metabolismo , Animais , Blastocladiella/crescimento & desenvolvimento , Células Cultivadas , Eletroforese em Gel de Poliacrilamida , Fungos/crescimento & desenvolvimento , Fungos/metabolismo , Fosforilação , Proteína S6 RibossômicaRESUMO
Ribosomal proteins of the aquatic fungus Blastocladiella emersonii were isolated and characterized on four different two-dimensional polyacrylamide gel electrophoresis systems. 40S and 60S ribosomal subunit proteins from zoospores were identified. The position of every protein was determined in each electrophoretic system using the "four-corners" method (Madjar et al., Molecular and General Genetics, 171: 121-134, 1979). Thirty-two and 39 proteins were identified in the 40S and 60S ribosomal subunits, respectively. The molecular weights of individual proteins in the 40S subunit ranged from 10 000 to 37 000, with a number-average molecular weight of 20 000. The molecular weight range for the 60S subunit was 13 000-51 000 with a number-average molecular weight of 21 000. Proteins from ribosomes of different cell types were compared and found to be qualitatively indistinguishable. The only consistent difference in the patterns of proteins was in the S6 protein of the 40S subunit, which is the major phosphoprotein of Blastocladiella ribosomes.
Assuntos
Blastocladiella/metabolismo , Quitridiomicetos/metabolismo , Proteínas Fúngicas/biossíntese , Proteínas Ribossômicas/biossíntese , Blastocladiella/análise , Blastocladiella/fisiologia , Eletroforese em Gel de Poliacrilamida/métodos , Proteínas Fúngicas/análise , Proteínas Ribossômicas/análise , Esporos Fúngicos/crescimento & desenvolvimentoRESUMO
The transference by conjugation of protease genetic information between Proteus mirabilis strains only occurs upon mobilization by a conjugative plasmid such as RP4 (Inc P group). Upon receiving the RP4 plasmid, the level of proteolytic activity of the protease-excreting P. mirabilis is reduced to about 50%. A similar phenomenon occurs when the protease character is mobilized by the RP4 plasmid from the above transconjugant to a non-protease-excreting recipient strain. The molecular mechanism underlying the interference of R plasmids with proteolytic activity remains to be elucidated but there is evidence suggesting that some alteration in the bacterial envelope might be involved.
Assuntos
Peptídeo Hidrolases/metabolismo , Proteus mirabilis/genética , Fatores R , Proteus mirabilis/enzimologiaRESUMO
A presenca de plasmidio R, em clones excretores e nao excretores da protease, de uma linhagem de Proteus mirabilis, confere maior sensibilidade ao desoxicolato de sodio
Assuntos
Humanos , Proteus mirabilis , Fatores R , Ácido DesoxicólicoRESUMO
Drogas curagenicas, como brometo de etidio acriflavina e mitomicina C, aumentam grandemente, a conversao de celulas excretoras de protease instaveis de Proteus mirabilis em celulas nao excretoras. Esse efeito nao ocorre sobre celulas excretoras estaveis de protease. A rifampicina apenas seleciona celulas protease-negativas, por eliminacao preferencial de celulas excretoras.Temperaturas superiores a fisiologica nao sao efetivas na perda de excrecao de protease em linhagens de P. mirabilis que excretam protease de maneira instavel