RESUMO
The genes encoding the two structural subunits of Escherichia coli hydrogenase 2 (HYD2) have been cloned and sequenced. They occur in an operon (hyb) which contains seven open reading frames. An hyb deletion mutant (strain AP3) failed to grown on dihydrogen-fumarate medium and also produced very low levels of HYD1. All seven open reading frames are required for restoration of wild-type levels of active HYD2 in AP3. The hyb operon was mapped at 65 min on the E. coli chromosome.
Assuntos
Escherichia coli/genética , Hidrogenase/genética , Óperon , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Análise Mutacional de DNA , Escherichia coli/enzimologia , Genes Bacterianos , Teste de Complementação Genética , Hidrogenase/química , Hidrogenase/metabolismo , Dados de Sequência Molecular , Fenótipo , Análise de Sequência de DNARESUMO
DNA encompassing the structural genes of an Escherichia coli [NiFe] hydrogenase has been cloned and sequenced. The genes were identified as those encoding the large and small subunits of hydrogenase isozyme 1 based on NH2-terminal sequences of purified subunits (kindly provided by K. Francis and K. T. Shanmugam). The structural genes formed part of a putative operon that contained four additional open reading frames. We have designated the operon hya and the six open reading frames hyaA through F. hyaA and hyaB encode the small and large structural subunits, respectively. The nucleotide-derived amino acid sequence of hyaC has a calculated molecular mass of 27.6 kilodaltons, contains 20% aromatic residues, and has four potential membrane-spanning regions. Open reading frames hyaD through F could encode polypeptides of 21.5, 14.9, and 31.5 kilodaltons, respectively. These putative peptides have no homology to other reported protein sequences, and their functions are unknown.
Assuntos
Clonagem Molecular , Escherichia coli/genética , Hidrogenase/genética , Óperon , Sequência de Aminoácidos , Sequência de Bases , Southern Blotting , Membrana Celular/enzimologia , Escherichia coli/enzimologia , Genes Bacterianos , Substâncias Macromoleculares , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Conformação Proteica , Mapeamento por Restrição , Homologia de Sequência do Ácido NucleicoRESUMO
Batch cultures of Desulfovibrio vulgaris stored at 32 degrees C for 10 months have been found to retain 50% of the hydrogenase activity of a 1-day culture. The hydrogenase found in old cultures needs reducing conditions for its activation. Viable cell counts are negative after 6 months, showing that the hydrogenase activity does not depend on the presence of viable cells. These observations are of importance in the understanding of anaerobic biocorrosion of metals caused by depolarization phenomena.
