RESUMO
Changes in the amount of oligopeptide binding protein (OppA) in spontaneous kanamycin-resistant mutants of Escherichia coli were investigated. Among 20 colonies obtained from 10(8) cells cultured in the presence of 20 microgram of kanamycin/ml, 1 colony had no detectable OppA and 7 colonies were mutants with reduced amounts of OppA. Sensitivity of wild-type cells to kanamycin increased slightly by transformation of the oppA gene, but the sensitivity of the mutants increased greatly by the transformation. A mutant with no OppA was found to be a nonsense mutant of the oppA gene at amino acid position 166. In a mutant having a reduced level of OppA, the reduction was due to the decrease in OppA synthesis at the translational level. These mutants were also resistant to other aminoglycoside antibiotics, including streptomycin, neomycin, and isepamicin. Isepamicin uptake activities decreased greatly in these two kinds of mutants. The results support the proposition that aminoglycoside antibiotics are transported into cells by the oligopeptide transport system, and that transport is an important factor for spontaneous resistance to aminoglycoside antibiotics.
Assuntos
Antibacterianos/farmacologia , Proteínas de Transporte/genética , Escherichia coli/efeitos dos fármacos , Resistência a Canamicina/genética , Lipoproteínas/genética , Mutagênese , Aminoácidos/análise , Antibacterianos/metabolismo , Proteínas de Bactérias , Transporte Biológico/genética , Proteínas de Transporte/biossíntese , Regulação para Baixo , Escherichia coli/genética , Proteínas de Escherichia coli , Gentamicinas/metabolismo , Canamicina/metabolismo , Canamicina/farmacologia , Lipoproteínas/biossíntese , Peptídeos/metabolismo , Poliaminas/análiseRESUMO
An alpha-amylase gene from Streptomyces sp WL6 was cloned on a 3.1kb DNA fragment, which was completely sequenced. The 3088 nucleotide sequence obtained contains three putative coding regions in the same orientation. The one corresponding to the structural region of the alpha-amylase gene has a deduced amino acid sequence of 459 residues, showing up to 71% identity to other alpha-amylases. An incomplete ORF was identified upstream the alpha-amylase gene, and the deduced product presents some homology to proteins involved in catabolic regulation.
Assuntos
Genes Bacterianos , Streptomyces/enzimologia , Streptomyces/genética , alfa-Amilases/genética , Sequência de Aminoácidos , Sequência de Bases , Sítios de Ligação , Códon , Hidrólise , Dados de Sequência Molecular , Plasmídeos/química , Plasmídeos/genética , Regiões Promotoras Genéticas , Ribossomos/metabolismo , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido Nucleico , Amido/metabolismoRESUMO
The induction of rho- "petite" mutants by guanidine hydrochloride (GuHCl) is inhibited in several conditions. Anaerobiosis inhibited the induction either with or without cell multiplication. Both nalidixic acid (NA) and cycloheximide (CH) inhibited the induction of mutants. On the other hand, chloramphenicol (CAP) produced a dual effect: at low concentration it stimulated, at high concentration it inhibited, the induction. The effect of these different inhibitors on the transformation of rho+ mother cells into rho- by GuHCl is discussed.
Assuntos
Guanidinas/farmacologia , Mutação/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos dos fármacos , Anaerobiose , Cloranfenicol/farmacologia , Cicloeximida/farmacologia , Diploide , Guanidinas/antagonistas & inibidores , Mutagênicos , Ácido Nalidíxico/farmacologiaRESUMO
Nonchromosomal "petites" can be produced in Saccharomyces cerevisiae by treatment with sodium dodecyl sulfate, an anionic surface active agent.
