Identification of a novel DNA-binding protein from Mycobacterium bovis bacillus Calmette-Guérin.

A novel DNA-binding protein expressed (8-10% in total protein) in Mycobacterium bovis bacillus Calmette-Guérin was observed. This protein was designated mycobacterial DNA-binding protein 1 (MDP1). MDP1 recognized bases, sugar moieties, phosphate-backbone on DNA and preferentially bound to DNA guanine and cytosine. In the gel retardation assay, MDP1 preferentially bound to closed circular plasmid DNA than open circular and linear form plasmid DNA and also bound to RNA. MDP1 formed a highly polymerized structure and localized not only in the nucleoid but also at the 50S ribosomal subunits and cell surface. MDP1 was conserved in Mycobacterium thus far examined and the expression was enhanced in stationary growth phases. These results will provide a reasonable basis for further study of the function of MDP1 in living mycobacteria.