Excretion of ammonium by a nifL mutant of Azotobacter vinelandii fixing nitrogen.
AUTOR(ES)
Bali, A
RESUMO
A mutation in the gene upstream of nifA in Azotobacter vinelandii was introduced into the chromosome to replace the corresponding wild-type region. The resulting mutant, MV376, produced nitrogenase constitutively in the presence of 15 mM ammonium. When introduced into a nifH-lacZ fusion strain, the mutation permitted beta-galactosidase production in the presence of ammonium. The gene upstream of nifA is therefore designated nifL because of its similarity to the Klebsiella pneumoniae nifL gene in proximity to nifA, in mutant phenotype, and in amino acid sequence of the gene product. The A. vinelandii nifL mutant MV376 excreted significant quantities of ammonium (approximately 10 mM) during diazotrophic growth. In contrast, ammonium excretion during diazotrophy was much lower in a K. pneumoniae nifL deletion mutant (maximum, 0.15 mM) but significantly higher than in NifL+ K. pneumoniae. The expression of the A. vinelandii nifA gene, unlike that of K. pneumoniae, was not repressed by ammonium.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=195662Documentos Relacionados
- The Basis of Ammonium Release in nifL Mutants of Azotobacter vinelandii
- Mutant Forms of the Azotobacter vinelandii Transcriptional Activator NifA Resistant to Inhibition by the NifL Regulatory Protein
- A crucial arginine residue is required for a conformational switch in NifL to regulate nitrogen fixation in Azotobacter vinelandii
- Ammonium and methylammonium transport by the nitrogen-fixing bacterium Azotobacter vinelandii.
- Genetic analysis of Azotobacter vinelandii mutant strains unable to fix nitrogen.