MtFtsX a predicted membrane domain of ABC transporter complex MtFtsEX of Mycobacterium tuberculosis interacts with the cell division protein MtFtsZ.

Abstract

Bacterial cytokinesis is orchestrated by a complex of dozen of proteins called 'divisome' at the mid-cell site. FtsZ, the eukaryotic tubulin homolog, localizes to the mid-cell site where it polymerizes and forms a cytokinetic Z-ring. The Z-ring acts as a docking platform for other proteins to localize. In model organisms, Escherichia coli and Bacillus subtilis, FtsZ is known to interact with several proteins. The role of few of these interactions is known, while of others is yet to be studied. In Mycobacterium tuberculosis, the cell division and its regulation are poorly studied. Although, most of the divisome proteins are conserved in M. tuberculosis, surprisingly the homologues of the protein factors required for membrane association of Z-ring and its stabilization are absent. In E. coli FtsE and FtsX, the constituent ATPase and membrane domains of the ABC transporter complex, localize to the Z-ring immediately after Z-ring stabilizing proteins, ZipA and FtsA. Therefore, investigation of the interaction between MtFtsX and MtFtsZ is demanding. Bacterial two-hybrid system was used to identify the interaction between MtFtsE and MtFtsZ. This interaction was further confirmed by biochemical methods of Ni2+-NTA agarose pull-down and coimmunoprecipitation. Here, we demonstrated that MtFtsX interacts with MtFtsZ in vivo and ex-vivo. Further, we showed that self-interacting MtFtsX interacts with MtFtsE. However, we did not find any interaction between MtFtsE and MtFtsZ. These results suggest that the membrane domain MtFtsX of the ABC transporter complex 'MtFtsEX' might be the membrane-tethering and stabilizing factor for Z-ring in M. tuberculosis.