AI Article Synopsis

  • Genetic analyses showed that HvrA negatively regulates the transcription of nifH and nifB1 but not rpoN, nifA1, or nifA2 in Rhodobacter capsulatus.
  • Despite mutations in ntrC being crucial for N(2) fixation, they do not affect hvrA expression, and HvrA levels remain consistent regardless of ammonium presence.
  • Competitive gel retardation studies revealed that HvrA preferentially binds to the nifH promoter region.

Article Abstract

Genetic analyses based on chromosomal lac fusions to nitrogen fixation (nif) genes demonstrated that NifA-dependent transcriptional activation of expression of Rhodobacter capsulatus nifH and nifB1 was negatively modulated by HvrA, whereas regulation of rpoN, nifA1, and nifA2 was independent of HvrA. Expression of hvrA itself was not influenced by a mutation in ntrC, which is absolutely essential for N(2) fixation. Furthermore, HvrA accumulated to comparable levels in the presence and absence of ammonium, suggesting that the amount of HvrA in the cells does not differ under nitrogenase-repressing or -derepressing conditions. In addition, competitive gel retardation studies with HvrA-His(6) purified from R. capsulatus were carried out, demonstrating preferential binding of HvrA to the nifH promoter region.

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http://dx.doi.org/10.1111/j.1574-6968.2002.tb11429.xDOI Listing

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