Analysis of the nucleotide sequence of a gene cloned from a Mycobacterium tuberculosis H37Rv genomic library predicted a 339-amino-acid protein with an M(r) of 37656. The protein exhibited significant homology with the Cfad, FapR and Rns proteins from different enterotoxigenic strains of Escherichia coli, VirF protein of Shigella and VirFy protein of Yersinia, all of which regulate virulence-associated genes.