A Lipid‐Anchored Binding Protein is a Component of an ATP‐Dependent Cellobiose/Cellotriose‐Transport System from the Cellulose Degrader Streptomyces reticuli

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Abstract
During cultivation in the presence of cellobiose or crystalline cellulose, Streptomyces reticuli expresses an inducible uptake system that transports cellobiose (Km, 4 μM), 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 (Kd, 1.5 μM) 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.