Interaction of Mycobacterium tuberculosis ESAT-6 protein with ADAM9 protein

The ESAT-6 protein of Mycobacterium tuberculosis (M. tb) is an important structural and functional protein, which has been known to be involved in the virulence, pathogenesis as well as proliferation of the pathogen; however, how ESAT-6 protein interact with host protein is still unclear. In order to study the function of the M. tuberculosis protein ESAT-6 in the infection process, we searched for host proteins that interact with this secreted mycobacterial protein. Using a yeast two-hybrid system we identified the ADAM9 (a disintegrin and metalloprotease) protein as a candidate to interact with ESAT-6. This interaction was further confirmed by protein overlay and surface plasmon resonance binding assay using recombinant ESAT-6 and ADAM9, and by GST pull-down analysis of the mycobacterial expressed ESAT-6 and ADAM9. The interaction domains were localized by yeast two-hybrid studies using truncated derivatives of ESAT-6 protein. The C-terminus of ESAT-6 binds to the ADAM9, Thus, the host protein ADAM9 represents a possible cellular receptor for the mycobacterial protein ESAT-6. This is the first report demonstrating the interaction of ADAM9 with a structural protein of M. tb.