Sequences of nifX, nifW, nifZ, nifB and two ORF in the Frankia nitrogen fixation gene cluster.
The actinomycete Frankia alni fixes N2 in root nodules of several non-leguminous plants. It is one of the few known N2-fixing members of the high-GC Gram+ lineage of prokaryotes. Thus, we have undertaken a study of its nitrogen fixation gene (nif) organization to compare with that of the more extensively characterized proteobacteria. A cosmid (pFN1) containing the nif region of Fa CpI1 was isolated from a cosmid library using the nifHDK genes of Fa CpI1 as a probe. A 4.5-kb BamHI fragment that mapped downstream from the previously characterized nifHDK genes was cloned and sequenced. Based on nt and aa sequence similarities to nif from other N2-fixing bacteria, eight ORF were identified and designated nifX, orf3, orf1, nifW, nifZ, nifB, orf2 and nifU. A region that hybridized to Rhizobium meliloti and Klebsiella pneumoniae nifA did not appear to contain a nifA-like gene. We have revised the map of the Fa nif region to reflect current information.
Harriott
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Department of Molecular and Cell Biology, University of Connecticut, Storrs 06268-3044, USA.
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Benson
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D000192:Actinomycetales / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D005810:Multigene Family; D009586:Nitrogen Fixation / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D016366:Open Reading Frames