Autoregulation of nitrogenase expression in Klebsiella pneumoniae

• Published in: Microbiology (Society for General Microbiology) Vol. 140; no. 8; pp. 1917 - 1925
• Main Authors: Hill, Susan, Kavanagh, Eugene P
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.08.1994; Society for General Microbiology
• Subjects: Anaerobiosis; Argon; Bacterial Proteins - biosynthesis; Bacterial Proteins - genetics; Bacteriology; Biological and medical sciences; Feedback; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial - drug effects; Genes, Bacterial; Genetics; Klebsiella pneumoniae; Klebsiella pneumoniae - enzymology; Klebsiella pneumoniae - genetics; Microbiology; Nitrogen - pharmacology; Nitrogen Fixation - genetics; Nitrogenase - biosynthesis; Nitrogenase - genetics; Recombinant Fusion Proteins - biosynthesis; Autoregulation; Enzyme; Nitrogen; Gene expression; Ferromolybdoprotein; Regulation(control); Nitrogenase; Nitrogen fixation; Bacteria; Repression derepression; Oxidoreductases; Klebsiella pneumoniae; Enterobacteriaceae
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/13500872-140-8-1917

Nitrogen Fixation Laboratory, University of Sussex, Brighton BN1 9RQ, UK ABSTRACT An investigation into the influence of N 2 on the expression of Klebsiella pneumoniae nitrogenase has led to a reassessment of the role of the nitrogenase MoFe protein in autoregulation. Anaerobic derepression of nitrogenase (C 2 H 2 -reducing) activity, of NifD and K polypeptides, and of nifH-lac expression, following the removal of excess NH + 4 , were greater under N 2 than Ar. This enhancement occurred in Nif + but not in Nif – strains, and in Nif + strains was prevented by C 2 H 2 , an inhibitor of N 2 fixation. Thus N 2 fixation is important for maintaining derepression. Derepression of nifH-lac under Ar in various Nif + and Nif – strains (including NifH – , NifD – , NifB – and NifL – mutants) and of wild-type lac under N 2 or Ar in a Nif + strain were measured to investigate the regulation. The mechanism regulating the enhancement under N 2 neither involved the MoFe protein of nitrogenase, as proposed by Dixon et al. (1980, Nature 286, 128-132), nor the nifL product, but was probably due to a general upgrading of the N status. Moreover, during batch growth limited by a non-repressing fixed N source, the levels of nifH-lac expression in the Nif + and Nif – strains suggested that the nifH gene product (or Fe protein) may have a positive autoregulatory function. Author for correspondence: Susan Hill. Tel: +44 273 678242. Fax: +44 273 678133. e-mail: SUSAN. HILL@BBSRC.AC.UK Keywords: Klebsiella pneumoniae , nitrogenase, anaerobic derepression, nifH-lac expression, autoregulation