Acts as a transcriptional regulator. Probably redox-responsive. The apo- but not holo-form probably binds DNA (By similarity). Affects the localization or efficiency of septum formation. Complemented by whiB2 of M.tuberculosis and whiB of S.coelicolor. Binds 1 [4Fe-4S] cluster per subunit. Following nitrosylation of the [4Fe-4S] cluster binds 1 [4Fe-8(NO)] cluster per subunit. Oligomeric in native gel electrophoresis. In exponential phase (at protein level). The Fe-S cluster can be nitrosylated by nitric oxide (NO). Upon Fe-S cluster removal intramolecular disulfide bonds are formed. Essential. In depletion experiments, individual cells are elongated and/or filamented, with diminished septum formation and aberrant septal placement. The septa that do form may be immature as cytokinesis does not occur. Has no effect on FtsZ accumulation. Cells are less viable, colonies are smaller and the mutant is non-acid-fast under conditions of acetamide withdrawal. In this protein one of the ligands for the Fe-S cluster may be provided by Asp-71 rather than Cys-67. Belongs to the WhiB family.