The Streptomyces coelicolor whiB gene encodes a small transcription factor-like protein dispensable for growth but essential for sporulation.

A non-sporulating mutant (whiB218) of Streptomyces coelicolor A3(2), which proved to contain a deletion of more than 5 kb of DNA including whiB, was complemented by a small cloned DNA fragment, deduced from DNA sequencing to encode a protein of only 87 amino acids. This protein would bear some similarities to transcription factors, including an acidic, somewhat amphipathic alpha-helical region predicted near its N-terminus, and a basic alpha-helical region predicted at its C-terminus. A point mutation (whiB70) giving a phenotype indistinguishable from that of the whiB218 deletion mutant would cause a leucine to proline change at the start of the latter region. The whiB homologue from the closely related species S. lividans differed at only one base from its S. coelicolor counterpart, and would specify an identical polypeptide.