title: The presence of five nifH-like sequences in Clostridium pasteurianum: sequence divergence and transcription properties.
abstract: The nifH gene encodes the iron protein (component II) of the nitrogenase complex. We have previously shown the presence in Clostridium pasteurianum of two nifH-like sequences in addition to the nifH1 gene which codes for a protein identical to the isolated iron protein. In the present study, we report that there are at least five nifH-like sequences in C. pasteurianum. DNA sequencing data indicate that the six nifH (nifH1) and nifH-like (nifH2, nifH3, nifH4, nifH5 and nifH6) sequences are not identical and vary from each other to different extents with sequence identity ranging between 68 to 99.9% within the nifH coding regions. Under normal N2-fixing growth conditions (molybdenum-containing medium), transcripts of nifH1 and most of the nifH-like sequences accumulate. The above results suggest the functioning of more than one "nifH" gene under N2-fixing growth conditions for C. pasteurianum. A common sequence was found around the -100 regions of all nif or nif-like transcription units. Sequences identical to or very similar to the consensus Escherichia coli promoter were found in the -35 and -10 regions.
authors.affiliation: Department of Anaerobic Microbiology, Virginia Polytechnic Institute and State University, Blacksburg 24061.
authors.forename: S Z
authors.initials: SZ
authors.lastname: Wang
authors.forename: J S
authors.initials: JS
authors.lastname: Chen
authors.forename: J L
authors.initials: JL
authors.lastname: Johnson
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003013:Clostridium / Q000235:genetics*; D004262:DNA Restriction Enzymes; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: D004262:DNA Restriction Enzymes