Cloning, nucleotide sequence, and regulation of the Bacillus subtilis nadB gene and a nifS-like gene, both of which are essential for NAD biosynthesis.
A number of Bacillus subtilis genes involved in NAD biosynthesis have been cloned and sequenced. One of the genes encodes a polypeptide homologous to Escherichia coli L-aspartate oxidase, and its mutation resulted in a nicotinic acid (Nic)-dependent phenotype; this gene was termed nadB. A second open reading frame (orf2) was found downstream of nadB, and an insertional plasmid separating orf2 and nadB also gave a Nic-dependent phenotype. This result suggests that orf2 may also be involved in NAD biosynthesis and that nadB and orf2 are in the same operon. Upstream of nadB was a third gene, transcribed in the opposite direction to that of nadB-orf2. The amino acid sequence derived from the third gene was quite similar to those derived from nifS genes of various nitrogen-fixing bacteria; therefore, the third gene was termed nifS. As with nadB and orf2, mutations in nifS also resulted in a Nic-dependent phenotype. The promoter regions of nadB and nifS overlapped each other and both contained -10 and -35 sequences which resemble those of E sigma A-type promoters. Transcription from both the nifS and nadB promoters, as well as expression of a nadB-lacZ fusion, was repressed by Nic. However, nadB transcription and nadB-lacZ expression were decreased, at most, only slightly by a deletion in nifS. The possible role of the nifS gene product in NAD biosynthesis is discussed.
Sun
D
D
Department of Biochemistry, University of Connecticut Health Center, Farmington 06030-3305.
Setlow
P
P
D000594:Amino Acid Oxidoreductases / Q000235:genetics*; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D009243:NAD / Q000096:biosynthesis / Q000235:genetics*; D009537:Nicotinamide Mononucleotide / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000235:genetics; D009586:Nitrogen Fixation / Q000235:genetics*; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C080001:nifS protein, Bacteria; D009243:NAD; D009537:Nicotinamide Mononucleotide; C002953:nicotinate mononucleotide; D000594:Amino Acid Oxidoreductases; C031955:L-aspartate oxidase, E coli