WhmD promotes the assembly of Mycobacterium smegmatis FtsZ (538.2)

FtsZ assembles into a ring like structure known as Z‐ring at the mid‐cell during cytokinesis. Several proteins are known to assist in the appropriate formation and functioning of the cytokinetic Z‐ring. WhmD, a Mycobacterium smegmatis protein, is essential for septum formation and bacterial cell division. Deletion of WhmD causes deformed septum formation and filamentation of Mycobacterium smegmatis. In the present study, we sought to determine the effect of WhmD on the assembly of Mycobacterium smegmatis FtsZ. Light scattering experiment showed that WhmD increased the assembly of Mycobacterium smegmatis FtsZ in vitro in a concentration dependent manner. Further, WhmD also increased the sedimentable polymerized mass of Mycobacterium smegmatis FtsZ. For example, the amount of FtsZ polymerized was increased by 54% in the presence of 1:1 WhmD and FtsZ. Under the conditions used, FtsZ formed thin filaments. Electron microscopic analysis suggested that WhmD enhanced the assembly and bundling of Mycobacterium smegmatis FtsZ filaments. In addition, WhmD increased the GTPase activity of Mycobacterium smegmatis FtsZ in vitro. For example, 6 µM WhmD increased the GTPase activity of 6 µM FtsZ by ~120%. The results indicated that WhmD may function as a positive regulator of the assembly of Mycobacterium smegmatis FtsZ.