Cloning and sequence analysis of the gene encoding the DNA polymerase I from Mycobacterium tuberculosis.

The polA gene (encoding DNA polymerase I) from Mycobacterium tuberculosis was cloned using an internal gene segment probe generated by PCR amplification of genomic DNA [Mizrahi et al., Gene 136 (1993) 287-290]. The gene encodes a polypeptide 904 amino acids (aa) in length that shares 89% identity with a 911-aa homologue from Mycobacterium leprae. The polypeptide has all of the primary structural elements necessary for DNA polymerase and 5'-3' exonuclease activity, but lacks the motifs required for an associated 3'-5' exonuclease (proofreading) activity.