Substrate induction and glucose repression of maltose utilization by Streptomyces coelicolor A3(2) is controlled by malR, a member of the lacl-galR family of regulatory genes.

malR of Streptomyces coelicolor A3(2) encodes a homologue of the Lacl/GalR family of repressor proteins, and is divergently transcribed from the malEFG gene cluster, which encodes components of an ATP-dependent transport system that is required for maltose utilization. Transcription of malE was induced by maltose and repressed by glucose. Disruption or deletion of malR resulted in constitutive, glucose-insensitive malE transcription at a level markedly above that observed in the parental malR+ strain, and overproduction of MalR prevented growth on maltose as carbon source. Consequently, MalR plays a crucial role in both substrate induction and glucose repression of maltose utilization. malR is expressed from a single promoter with transcription initiating at the first G of the predicted GTG translation start codon.