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

Authors


H. Schrempf, FB Biologie/Chemie, Universität Osnabrück, Barbarastrasse 11, D-49069 Osnabrück, Germany

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.

Abbreviations
CBP

cellobiose-binding protein

MalNEt

N-ethylmaleimide

PTS

phosphotransferase system

Ancillary

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