A LIPID-ANCHORED BINDING-PROTEIN IS A COMPONENT OF AN ATP-DEPENDENT CELLOBIOSE CELLOTRIOSE-TRANSPORT SYSTEM FROM THE CELLULOSE DEGRADER STREPTOMYCES-RETICULI/

During cultivation in the presence of cellobiose or crystalline cellul ose, Streptomyces reticuli expresses an inducible uptake system that t ransports cellobiose (K-m, 4 mu-M), cellotriose and, to a lesser degre e, cellotetraose and cellopentaose. Cellobiose uptake is dependent on ATP and inhibited by N-ethylmaleimide. A binding protein was identifie d in its palmitylated form in the cytoplasmic membrane of mycelia. It could be extracted with the detergent Triton X-100 and purified by two subsequent anion-exchange chromatographies. It showed highest affinit y (K-d, 1.5 mu M) for cellobiose and cellotriose. The data suggest tha t cellobiose/cellotriose uptake is mediated by a membrane-anchored lip oprotein as a component of an ATP-binding-cassette-transporter system.