Involvement of NtcB, a LysR family transcription factor, in nitrite activation of the nitrate assimilation operon in the cyanobacterium Synechococcus sp. strain PCC 7942.
AUTOR(ES)
Aichi, M
RESUMO
Nitrite, either exogenously supplied or endogenously generated by nitrate reduction, activates transcription of the nitrate assimilation operon (nirA-nrtABCD-narB) in Synechococcus sp. strain PCC 7942 cells treated with L-methionine-DL-sulfoximine (an inhibitor of glutamine synthetase), in which there is no negative feedback resulting from fixation of the ammonium generated by nitrite reduction (Kikuchi et al., J. Bacteriol. 178:5822-5825, 1996). Other transcription units related to nitrogen assimilation, i.e., the nirB-ntcB operon, glnA, and ntcA, were not activated by nitrite. Nitrite did not activate nirA operon transcription in a mutant with a deletion of ntcB, an ammonium-repressible gene encoding a LysR-type DNA-binding protein. Introduction of plasmid-borne ntcB into the ntcB deletion mutant restored the response of the cells to nitrite, indicating that NtcB activates the nirA operon in response to nitrite. Supplementation of nitrite or nitrate to nitrogen-starved cultures of the wild-type strain, but not of the ntcB deletion mutant, caused activation of the nirA operon without L-methionine-DL-sulfoximine treatment of the cells. The results suggested that the positive-regulation mechanism of nirA operon transcription plays a role in rapid adaptation of nitrogen-starved cells to changing availability of nitrate and nitrite.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=179310Documentos Relacionados
- Role of NtcB in Activation of Nitrate Assimilation Genes in the Cyanobacterium Synechocystis sp. Strain PCC 6803
- cis-Acting Sequences Required for NtcB-Dependent, Nitrite-Responsive Positive Regulation of the Nitrate Assimilation Operon in the Cyanobacterium Synechococcus sp. Strain PCC 7942
- cis-Acting Sequences Required for NtcB-Dependent, Nitrite-Responsive Positive Regulation of the Nitrate Assimilation Operon in the Cyanobacterium Synechococcus sp. Strain PCC 7942
- Two functional psbD genes in the cyanobacterium Synechococcus sp. strain PCC 7942.
- Identification and cloning of a regulatory gene for nitrogen assimilation in the cyanobacterium Synechococcus sp. strain PCC 7942.