Cloning and characterization of the gene for immunogenic protein MPB64 of Mycobacterium bovis BCG.

The gene for immunogenic protein MPB64 found in culture filtrates of only Mycobacterium tuberculosis and some strains of Mycobacterium bovis BCG was cloned by using a single-probe method and was sequenced. The gene analysis revealed that the structural gene for MPB64 consisted of 618 base pairs, and its deduced molecular weight was 22,400. Twenty-two amino acids for a putative signal peptide and 205 amino acids for the MPB64 protein were observed. In the coding region, the third letter of the codon showed a biased codon and a high G+C content (78.5%). The gene was expressed in Escherichia coli by using an E. coli expression vector. The product showed migration similar to that of the authentic MPB64 protein by electrophoresis and reacted with the polyclonal and the monoclonal antibodies raised against the MPB64 protein. The strict specificity of MPB64 could be applied to immunodiagnosis of tuberculosis.