Synthesis of the Streptomyces lividansmaltodextrin ABC transporter depends on the presence of the regulator MalR

During growth with maltotriose or amylose, Streptomyces lividansand Streptomyces coelicolorA3(2) synthesize a maltodextrin uptake system with highest specificity for maltotriose. The transport activity is absent in mutants of S. coelicolorA3(2) lacking a functional MalE binding protein. Cloning and sequencing data suggest that the maloperon of S. coelicolorA3(2) corresponds to the one of S. lividansand that the deduced S. lividansReg1 amino acid sequence is identical to that of MalR from S. coelicolorA3(2). It can be concluded that both strains have the same ABC transport system for maltodextrins. The S. lividans malR was cloned in Escherichia coliin frame with six histidine‐encoding codons. The resulting, purified 6HisMalRSIwas shown to bind to two motifs within the S. lividans malR–malE intergenic region and to dissociate in the presence of maltopentaose.