A dominant-negative regulator of endogenous whiB2 expression. Low level expression in liquid culture in M.smegmatis leads to elongated and highly branched cells, with multiple nucleoids, similar to the effects seen in deletion experiments for whiB2 in M.smegmatis, as well as loss of acid-fastness. High level expression is lethal. Represses expression of endogenous whiB2. The apo-form binds to the whiB2 promoter found in M.tuberculosis. M.smegmatis cells expressing this protein will not grow on plates. Low level expression in M.smegmatis leads to superinfection exclusion, possibly via modification to the cell wall. Binds 1 [4Fe-4S] cluster per subunit. Contains 1 [2Fe-2S] cluster after reconstitution of overexpressed protein from E.coli. Following nitrosylation of the [4Fe-4S] cluster binds 1 [4Fe-8(NO)] cluster per subunit. Forms homodimers in the absence of a reducing agent. Expressed in the early phase of the viral replicative cycle. The iron-sulfur cluster is sensitive to air and oxidizing agents; degradation is complete in 3 hours upon exposure to air. The Fe-S cluster can be nitrosylated by nitric oxide (NO). Upon Fe-S cluster removal intramolecular disulfide bonds are formed. Dispensible for viral growth in M.smegmatis strain ATCC 700084 / mc(2)155. Belongs to the WhiB family.