Structural analysis of semi-specific oligosaccharide recognition by a cellulose-binding protein of thermotoga maritima reveals adaptations for functional diversification of the oligopeptide periplasmic binding protein fold.

Published

Journal Article

Periplasmic binding proteins (PBPs) constitute a protein superfamily that binds a wide variety of ligands. In prokaryotes, PBPs function as receptors for ATP-binding cassette or tripartite ATP-independent transporters and chemotaxis systems. In many instances, PBPs bind their cognate ligands with exquisite specificity, distinguishing, for example, between sugar epimers or structurally similar anions. By contrast, oligopeptide-binding proteins bind their ligands through interactions with the peptide backbone but do not distinguish between different side chains. The extremophile Thermotoga maritima possesses a remarkable array of carbohydrate-processing metabolic systems, including the hydrolysis of cellulosic polymers. Here, we present the crystal structure of a T. maritima cellobiose-binding protein (tm0031) that is homologous to oligopeptide-binding proteins. T. maritima cellobiose-binding protein binds a variety of lengths of beta(1-->4)-linked glucose oligomers, ranging from two rings (cellobiose) to five (cellopentaose). The structure reveals that binding is semi-specific. The disaccharide at the nonreducing end binds specifically; the other rings are located in a large solvent-filled groove, where the reducing end makes several contacts with the protein, thereby imposing an upper limit of the oligosaccharides that are recognized. Semi-specific recognition, in which a molecular class rather than individual species is selected, provides an efficient solution for the uptake of complex mixtures.

Full Text

Duke Authors

Cited Authors

  • Cuneo, MJ; Beese, LS; Hellinga, HW

Published Date

  • November 27, 2009

Published In

Volume / Issue

  • 284 / 48

Start / End Page

  • 33217 - 33223

PubMed ID

  • 19801540

Pubmed Central ID

  • 19801540

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

Digital Object Identifier (DOI)

  • 10.1074/jbc.M109.041624

Language

  • eng

Conference Location

  • United States