mbiA

MbiA (also known as htgA/htpY) is a small (161 aa) uncharacterized orphan protein in E. coli K12 that arose by overprinting (de novo gene birth) within the antisense strand of the yaaW gene. It was originally proposed to be a heat shock gene regulated by sigma-32, but this was later refuted by genome-wide regulon analysis (PMID:16818608). The protein has no recognizable InterPro domains or known molecular function. The gene name mbiA (modifier of biofilm) derives from its Salmonella orthologue, and strand-specific mutagenesis shows differential biofilm phenotypes (PMID:24111745), though the overlapping yaaW gene complicates functional attribution. The MbiA protein has not been directly detected at the protein level (PE 2, evidence at transcript level only). Full-length mbiA is restricted to Escherichia and Shigella, and shows evidence of purifying selection despite being nonessential.