Influence of nar (nitrate reductase) genes on nitrate inhibition of formate-hydrogen lyase and fumarate reductase gene expression in Escherichia coli K-12.
AUTOR(ES)
Stewart, V
RESUMO
In Escherichia coli, aerobiosis inhibits the synthesis of enzymes for anaerobic respiration (e.g., nitrate reductase and fumarate reductase) and for fermentation (e.g., formate-hydrogen lyase). Anaerobically, nitrate induces nitrate reductase synthesis and inhibits the formation of both fumarate reductase and formate-hydrogen lyase. Previous work has shown that narL+ is required for the effects of nitrate on synthesis of both nitrate reductase and fumarate reductase. Another gene, narK (whose function is unknown), has no observable effect on formation of these enzymes. We report here our studies on the role of nar genes in fumarate reductase and formate-hydrogen lyase gene expression. We observed that insertions in narX (also of unknown function) significantly relieved nitrate inhibition of fumarate reductase gene expression. This phenotype was distinct from that of narL insertions, which abolished this nitrate effect under certain growth conditions. In contrast, insertion mutations in narK and narGHJI (the structural genes for the nitrate reductase enzyme complex) significantly relieved nitrate inhibition of formate-hydrogen lyase gene expression. Insertions in narL had a lesser effect, and insertions in narX had no effect. We conclude that nitrate affects formate-hydrogen lyase synthesis by a pathway distinct from that for nitrate reductase and fumarate reductase.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=211474Documentos Relacionados
- Identification and expression of genes narL and narX of the nar (nitrate reductase) locus in Escherichia coli K-12.
- Structure of genes narL and narX of the nar (nitrate reductase) locus in Escherichia coli K-12.
- In vivo requirement of integration host factor for nar (nitrate reductase) operon expression in Escherichia coli K-12.
- Requirement of Fnr and NarL functions for nitrate reductase expression in Escherichia coli K-12.
- Fnr, NarP, and NarL Regulation of Escherichia coli K-12 napF (Periplasmic Nitrate Reductase) Operon Transcription In Vitro