Cloning, Sequencing and Expression in Escherichia coli of the Gene for α Antigen from Mycobacterium scrofulaceum

The gene for the extracellular a antigen of Mycobacterium scrofulaceum (S‐α) was cloned by using the α antigen gene fragments of Mycobacterium bovis BCG as probes. The complete nucleotide sequence was determined. The gene was expressed in Escherichia coli. The gene encodes 330 amino acids, including 40 amino acids for the signal peptide, followed by 290 amino acids for the mature protein. The deduced amino acid sequences were highly homologous to the α antigen of the species of other mycobacteria. Interestingly, the a antigens of MAIS complex (Mycobacterium avium—Mycobacterium intracellulare—M. scrofulaceum) were closely homologous even at the C‐terminal regions which were variable among those of M. bovis BCG, Mycobacterium leprae and Mycobacterium kansasii.