Mutational analysis of nitrate regulatory gene narL in Escherichia coli K-12.
J Bacteriol
; 173(14): 4424-32, 1991 Jul.
Article
en En
| MEDLINE
| ID: mdl-2066339
ABSTRACT
The narL gene product, NarL, is the nitrate-responsive regulator of anaerobic respiratory gene expression. We used genetic analysis of narL mutants to better understand the mechanism of NarL-mediated gene regulation. We selected and analyzed seven nitrate-independent narL mutants. Each of three independent, strongly constitutive mutants had changes of Val-88 to Ala. The other four mutants were weakly constitutive. The narL505(V88A) allele was largely dominant to narL+, while narX+ had a negative influence on its constitutive phenotype, suggesting that NarX may play a negative role in nitrate regulation. We also constructed two narL mutations that are analogous to previously characterized constitutive degU alleles. The first, narL503(H15L), was a recessive null allele. The second, narL504(D110K), functioned essentially as wild type but was dependent on narX+ for full activity. We changed Asp-59 of NarL, which corresponds to the site of phosphorylation of other response regulators, to Asn. This change, narL502(D59N), was a recessive null allele, which is consistent with the hypothesis that NarL requires phosphorylation for activation. Finally, we tested the requirement for molybdate on regulation in a narL505(V88A) strain. Although narL505(V88A) conferred some nitrate-independent expression of fdnGHI (encoding formate dehydrogenase-N) in limiting molybdate, it required excess molybdate for full induction both in the absence and in the presence of nitrate. This finding suggests that narL505(V88A) did not confer molybdate-independent expression of fdnGHI.
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1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas Bacterianas
/
Genes Reguladores
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Mutagénesis Sitio-Dirigida
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Proteínas de Escherichia coli
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Proteínas de Unión al ADN
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Escherichia coli
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Genes Bacterianos
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Nitratos
Idioma:
En
Revista:
J Bacteriol
Año:
1991
Tipo del documento:
Article