Energetics of lectin-carbohydrate binding. A microcalorimetric investigation of concanavalin A-oligomannoside complexation.

Published

Journal Article

Despite years of study, a comprehensive picture of the binding of the lectin from Canavalia ensiformis, concanavalin A, to carbohydrates remains elusive. We report here studies on the interaction of concanavalin A with methyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside, the minimum carbohydrate epitope that completely fills the oligosaccharide binding site, and the two conceptual disaccharide "halves" of the trisaccharide, methyl 3-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside and methyl 6-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside, using titration microcalorimetry. In all cases the interaction of protein and carbohydrate is enthalpically driven, with an unfavorable entropic contribution. The choice of concentration scales has an important impact on both the magnitude and, in some cases, the sign of the entropic component of the free energy of binding. The thermodynamic data suggest binding of the two disaccharides may take place in distinct sites, as opposed to binding in a single high affinity site. In contrast to carbohydrate-antibody binding, delta Cp values were small and negative, pointing to possible differences in the motifs used by the two groups of proteins to bind carbohydrates. The thermodynamic data are interpreted in terms of solvent reorganization. Cooperativity during lectin-carbohydrate binding was also investigated. Significant cooperativity was observed only for binding of the trisaccharide, and gave a Hill plot coefficient of 1.3 for dimeric protein.

Full Text

Duke Authors

Cited Authors

  • Williams, BA; Chervenak, MC; Toone, EJ

Published Date

  • November 1992

Published In

Volume / Issue

  • 267 / 32

Start / End Page

  • 22907 - 22911

PubMed ID

  • 1429640

Pubmed Central ID

  • 1429640

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

International Standard Serial Number (ISSN)

  • 0021-9258

Language

  • eng