Higher order assembling of the mycobacterial essential polar growth factor DivIVA/Wag31

Abstract

How proteins localize at the pole remains an enigma. DivIVA/Wag31, which is an essential pole organizing protein in mycobacteria, can assemble at the negatively curved side of the membrane at the growing pole to form a higher order structural scaffold for maintaining cellular morphology and localizing various target proteins for cell-wall biogenesis. A single-site phosphorylation in Wag31 is linked to the regulation of peptidoglycan biosynthesis for optimal mycobacterial growth. The structural organization of polar scaffold formed by coiled-coil rich Wag31, which is a target for anti-tubercular agent amino-pyrimidine sulfonamide, remains to be determined. Here, we report biophysical characterizations of a phospho-mimetic (T73E) and a phospho-ablative (T73A) form of mycobacterial Wag31 using circular dichroism, small angle solution X-ray scattering and atomic force microscopy. While data obtained from both variants of Wag31 in solution states suggested formation of alpha-helical, large, elongated particles, their structural organizations were different. Atomic force microscopic images of Wag31 indicate polymer formation, with occasional curving, sharp bending and branching. Observed structural features in this first view of the polymeric forms of Wag31 suggest a basis for higher order network scaffold formation for polar protein localization.