Sequence and characterization of the glyceraldehyde-3-phosphate dehydrogenase of Mycobacterium avium: correlation with an epidermal growth factor binding protein.

ABSTRACT

Mycobacterium avium is a common pathogen in AIDS patients. The extracellular environment within the granuloma shown to support mycobacterial growth is in the caseous fluid. Previous work demonstrated that the presence of human epidermal growth factor (EGF), which is found in the tissue of chronic granulomous lesions, increases the growth rate of M. avium and Mycobacterium tuberculosis. Previously, a protein capable of binding recombinant human EGF (rEGF) in a western blot was identified with homology to glyceraldehyde-3-phosphate dehydrogenase (GAP) in both M. avium and M. tuberculosis but not Mycobacterium smegmatis. Surface GAPs have been identified in group A Streptococcus, enteropathogenic Escherichia coli, Candida albicans and Schistosoma mansoni. We have cloned the gap gene of M. avium. M. avium GAP has high homology with M. tuberculosis GAP. The protein was also expressed in M. smegmatis, conveying the ability to bind rEGF, but no growth increase was observed in 7H9 broth in the presence of rEGF up to 500 ng/ml. Only one copy of the GAP gene was identified in M. avium These results contribute to the understanding of M. avium pathogenesis by characterizing its interaction with a host protein present in the site of infection.