All three surface tryptophans in Type IIa cellulose binding domains play a pivotal role in binding both soluble and insoluble ligands

Nagy, Tibor and Simpson, Peter and Williamson, Michael P. and Hazlewood, Geoffrey P. and Gilbert, Harry J. and Orosz, László (1998) All three surface tryptophans in Type IIa cellulose binding domains play a pivotal role in binding both soluble and insoluble ligands. FEBS Letters, 429 (3). pp. 312-316. ISSN 00145793

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Abstract

The three surface tryptophans of the Type IIa cellulose binding domain of Pseudomonas fluorescens subsp. cellulosa xylanase A (CBDXYLA) were independently mutated to alanine, to create the mutants W13A, W49A and W66A. The three mutant proteins were purified, and their capacity to bind to a variety of ligands was determined. The mutant proteins have native-like structures but exhibited much weaker affinity for crystalline and amorphous cellulose and for cellohexaose than the wild type. These data indicate that all three tryptophans are important for binding to cellulose, and support a model in which the three tryptophans form an aromatic strip on the surface of the protein that binds to a single cellulose.

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