Synthesis of the Streptomyces lividans maltodextrin ABC transporter depends on the presence of the regulator MalR

During growth with maltotriose or amylose, Streptomyces lividans and Strept omyces coelicolor A3(2) synthesize a maltodextrin uptake system with highes t specificity for maltotriose. The transport activity is absent in mutants of S. coelicolor A3(2) lacking a functional MalE binding protein. Cloning a nd sequencing data suggest that the mal operon of S. coelicolor A3(2) corre sponds to the one of S. lividans and that the deduced S. lividans Reg1 amin o acid sequence is identical to that of MalR from S. coelicolor A3(2). It c an be concluded that both strains have the same ABC transport system for ma ltodextrins. The S. lividans malR was cloned in Escherichia coli in frame w ith six histidine-encoding codons. The resulting, purified 6HisMalR(Sl) was shown to bind to two motifs within the S. lividans malR-malE intergenic re gion and to dissociate in the presence of maltopentaose. (C) 2001 Federatio n of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.