A lipid-anchored binding protein is a component of an ATP-dependent cellobiose/cellotriose-transport system from the cellulose degrader Streptomyces reticuli

Abstract

During cultivation in the presence of cellobiose or crystalline cellulose, Streptomyces reticuli expresses an inducible uptake system that transports cellobiose (K-m, 4 mu-M), cellotriose and, to a lesser degree, cellotetraose and cellopentaose. Cellobiose uptake is dependent on ATP and inhibited by N-ethylmaleimide. A binding protein was identified 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 affinity (K-d, 1.5 mu M) for cellobiose and cellotriose. The data suggest that cellobiose/cellotriose uptake is mediated by a membrane-anchored lipoprotein as a component of an ATP-binding-cassette-transporter system.