2 NEW MEMBERS OF THE BIOB SUPERFAMILY - CLONING, SEQUENCING AND EXPRESSION OF BIOB GENES OF METHYLOBACILLUS-FLAGELLATUM AND CORYNEBACTERIUM-GLUTAMICUM

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