Novel post-translational modification system of NifF protein exists in Klebsiella pneumoniae which is different from that in Escherichia coli

Abstract

In Klebsiella pneumonia, regulation of the NifF protein (involved in N2-fixation) was not disscussed at the post-translational level until the recent discovery in Esherichia coli. Using a new K. pneumoniae strain MF, expressing high levels of NifF protein, we report a post-translational modification of NifF, which is different from that of E.coli. K. pneumoniae MF cultivated in L-broth and induced by IPTG had two forms of NifF protein (NifFα and NifFβ) that behaved similarly to the two forms of E. coli 71–18 NifF proteins (NifFI and NifFII) in non-SDS-PAGE. However, they behaved differently in response to the reduction by β-mercaptoethanol. NifFβ in the strain MF could not be reduced to NifFα, while NifFII from E. coli could be reduced to NifFI. Detection of NifF protein in different N2-fixing cells of K. pneumonia showed that only NifFβ existed, suggesting that this is the active form during N2-fixation. We conclude that post-translational control system of NifF during N2-fixation in K. pneumoniae is possibly different from that of E. coli. © Rapid Science Ltd. 1998