Regulation and characterization of protein products coded by the nif (nitrogen fixation) genes of Klebsiella pneumoniae

Abstract

Two hundred and thirty-five Nif- strains of Klebsiella pneumoniae were characterized by two-dimensional polyacrylamide gel electrophoresis. Forty-two of these strains were tested further by in vitro acetylene reduction assays. By these techniques, nine nif-coded polypeptides were identified, and eight of these were assigned to specific nif genes. Nitrogenase component I required nifK and nifD, which coded for the beta and alpha subunits, and nifB, -E, and -N were required for the iron-molybdenum cofactor, which is a part of the active site of nitrogenase. nifH coded for the structural protein of component II, and nifM and nifS products seemed to be necessary for the synthesis of an active component II. There were two genes, nifF and nifJ, that were required for N2 fixation in vivo but not for N2 fixation in vitro. There were at least two cases (nifE and nifN, nifK and nifD) of two proteins that seemed to require each other for stability in vivo. Regulation of N2 fixation is apparently complex, and this is reflected by the assignment of regulatory functions to the gene products of nifA, nifL, nifK, nifD, nifH, and NIFJ.

The bioenergetics of electron transport to nitrogenase

“…The products of nifF and nifJ have been implicated in electron transport to nitrogenase [66][67][68][69]. NifFand nifJ mutant strains have no nitrogenase activity in vivo, but do have activity in vitro with dithionite.…”

Identification and sequence of a nifJ‐like gene in Rhodospirillum rubrum: partial characterization of a mutant unaffected in nitrogen fixation

“…Detailed biochemical and genetic characterization of the entire physiological pathway of electron transfer to nitrogenase has only been reported in one organism, Klebsiella pneumoniae. In this diazotroph, pyruvate is oxidized by pyruvate:flavodoxin oxidoreductase, which transfers one electron to flavodoxin, the direct electron donor to dinitrogenase reductase (Bogusz et al, 1981;Deistung and Thorneley, 1986;Deistung et al, 1985;Hill and Kavanagh, 1980;Nieva-Gomez et al, 1980;Roberts et al, 1978;Shah et al, 1983;Wahl and Orme-Johnson, 1987). Both of these electron-transferring enzymes are specific for nitrogen fixation; pyruvate:flavodoxin oxidoreductase is encoded by nifJ, and flavodoxin by nifF (Arnold et al, 1988;Nieva-Gomez et al, 1980).…”

Molecular structure of the Frankia spp. nifD—K intergenic spacer and design of Frankia genus compatible primer

“…1988) and strains isolated from Purshia (Rosaceae), Coriariu (Coriariaceae) and Dutisca (Datiscaceae) (Mirza et al 1992) which are unable to reinfect those host plants. The n i p structural gene codes for the Fe protein (dinitrogenase reductase) and nifo-K for the two subunits of the MoFe protein (dinitrogenase), respectively (Roberts et al 1978). The nifK homologous region is in the same position relative to n i p and D in E alni ArZ3 strain (Normand et al 1988) as that found in most nitrogen fixing species where the nip-D-K genes are contiguous (Haselkom 1986).…”