This family consists of several glucitol operon activator (GutM) proteins. Expression of the glucitol (gut) operon in Escherichia coli is regulated by an unusual, complex system which consists of an activator (encoded by the gutM gene) and a repressor (encoded by the gutR gene) in addition to the cAMP-CRP complex (CRP, cAMP receptor protein). Synthesis of the mRNA, which initiates at the promoter specific to the gutR gene, occurs within the gutM gene. Expressional control of the gut operon appears to occur as a consequence of the antagonistic action of the products of the autogenously regulated gutM and gutR genes [1].

1: Positive and negative regulators for glucitol (gut) operon expression in Escherichia coli. Yamada M, Saier MH Jr; J Mol Biol 1988;203:569-583. PMID:3062173