A Novel Gene (narM) Required for Expression of Nitrate Reductase Activity in the Cyanobacterium Synechococcus elongatus Strain PCC7942
AUTOR(ES)
Maeda, Shin-ichi
FONTE
American Society for Microbiology
RESUMO
A new class of mutants deficient in nitrate assimilation was obtained from the cyanobacterium Synechococcus elongatus strain PCC7942 by means of random insertional mutagenesis. A 0.5-kb genomic region had been replaced by a kanamycin resistance gene cassette in the mutant, resulting in inactivation of two genes, one of which was homologous to the recently characterized cnaT gene of Anabaena sp. strain PCC7120 (J. E. Frías, A. Herrero, and E. Flores, J. Bacteriol. 185:5037-5044, 2003). While insertional mutation of the cnaT homolog did not affect expression of the nitrate assimilation operon or the activity of the nitrate assimilation enzymes in S. elongatus, inactivation of the other gene, designated narM, resulted in specific loss of the cellular nitrate reductase activity. The deduced NarM protein is a hydrophilic protein consisting of 161 amino acids. narM was expressed constitutively at a low level. The narM gene has its homolog only in the cyanobacterial strains that are capable of nitrate assimilation. In most of the cyanobacterial strains, narM is located downstream of narB, the structural gene of the cyanobacterial nitrate reductase, suggesting the functional link between the two genes. NarM is clearly not the structural component of the cyanobacterial nitrate reductase. The narM insertional mutant normally expressed narB, indicating that narM is not the transcriptional regulator of the structural gene of nitrate reductase. These results suggested that narM is required for either synthesis of the prosthetic group of nitrate reductase or assembly of the prosthetic groups to the NarB polypeptide to form functional nitrate reductase in cyanobacteria.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=374400Documentos Relacionados
- Signal Transduction Protein PII Is Required for NtcA-Regulated Gene Expression during Nitrogen Deprivation in the Cyanobacterium Synechococcus elongatus Strain PCC 7942
- Carbonic Anhydrase Activity Associated with the Cyanobacterium Synechococcus PCC7942 1
- Characterization of the dnaK Multigene Family in the Cyanobacterium Synechococcus sp. Strain PCC7942
- Light Control of hliA Transcription and Transcript Stability in the Cyanobacterium Synechococcus elongatus Strain PCC 7942
- Identification and characterization of two nitrogen-regulated genes of the cyanobacterium Synechococcus sp. strain PCC7942 required for maximum efficiency of nitrogen assimilation.
