Two new members of the bio B superfamily: cloning, sequencing and expression of bio B genes of Methylobacillus flagellatum and Corynebacterium glutamicum.

Cloning, characterization and expression of the bio B gene of the obligate methylotrophic bacterium, Methylobacillus flagellatum, are reported. A chromosomal fragment containing bio B has been isolated by complementation of a bio B- mutant of M. flagellatum. Nucleotide (nt) sequence analysis of this fragment revealed the presence of an open reading frame of 966 nt identified as bio B, which is the first gene of the M. flagellatum bio cluster. Gene bio B was expressed in Escherichia coli and M. flagellatum, resulting in efficient conversion of dethiobiotin to biotin. The Corynebacterium glutamicum bio B has also been cloned and sequenced. Comparison of the amino acid sequences derived from known bio B genes allowed us to identify four cysteines participating as putative ligands forming the [2Fe-2S] cluster. Genomic organization of the bio biosynthetic genes shows wide diversity in various bacteria. The results of the database screening suggested that bio B proteins belong to a superfamily of proteins, including biotin and lipoate synthases and some proteins with unidentified functions.