Genome for Denitrification

Deletion of the regulatory nirQ gene results simultaneously in a loss of the ability to reduce both nitrite and NO in P. stutzeri (Braun and Zumft, 1992). Nitrite reductase is synthesized and is active in vitro but nitric oxide reductase is synthesized in an inactive form. Although the exact function of the nirQ gene product is unknown, the gene encodes a protein homologous with the NtrC family of transcriptional activators (Zumft, 1993). 

The transcription of nir and nor genes in P. stutzeri (Cuypers and Zumft, 1992, 1993) and P. aeruginosa (Zimmermann et al., 1991) would appear to be controlled in part by homologs of the Fnr protein of E. coli (Guest, 1992) which is a redox sensitive, transcriptional activator. Fnr boxes (binding sequences) are located upstream from norC, nirM and nirS. It is likely therefore that Fnr-like proteins participate in a regulatory mechanism which derepresses the synthesis 

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