The Ligand-Binding Loops in the Tunicate C-type Lectin TC14 are Rigid

Poget, Sebastien F. and Freund, Stefan M. V. and Howard, Mark J. and Bycroft, Mark (2001) The Ligand-Binding Loops in the Tunicate C-type Lectin TC14 are Rigid. Biochemistry, 40 (37). pp. 10966-10972. ISSN 0006-2960. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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C-type lectin-like domains are very common components of extracellular proteins in animals. They bind to a variety of ligands, including carbohydrates, proteins, ice, and CaCO3 crystals. Their structure is characterized by long surface loops in the area of the protein usually involved in ligand binding. The C-type lectin TC14 from Polyandrocarpa misakiensis specifically binds to D-galactose by coordination of the sugar to a bound calcium atom. We have studied the dynamic properties of TC14 by measuring 15N longitudinal and transverse relaxation rates as well as [1H-15N] heteronuclear NOEs. Relaxation rates and heteronuclear NOE data for holo-TC14 show minimal variations, indicating that there is no substantial difference in rigidity between the elements of regular secondary structure and the extended surface loops. Anisotropic tumbling of the elongated TC14 dimer can account for the main fluctuations in relaxation rates. Loss of the bound calcium does not significantly alter the internal dynamics, suggesting that the stability of the loop region is intrinsic and not dependent on the coordination of the calcium ion. Chemical shift differences between the holo and apo form show that main structural changes occur in the calcium-binding site, but smaller structural changes are propagated throughout the molecule without affecting the overall fold. The disappearance of two resonances for residues following the conserved cis-proline 87 (which is located in the calcium-binding site) in the apo form indicates conformational change on an NMR time scale between the cis and trans configurations of this peptide bond in the absence of calcium. Possible implications of these findings for the ligand binding in C-type lectin-like domains are discussed.

Item Type: Article
Additional information: Comparative Study Journal Article Research Support, Non-U.S. Gov't United States
Uncontrolled keywords: Animals Binding Sites Galactose/metabolism Lectins/*chemistry/metabolism *Lectins, C-Type Ligands Models, Molecular Nuclear Magnetic Resonance, Biomolecular *Plant Lectins Pliability Protein Conformation *Urochordata
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Faculties > Science Technology and Medical Studies > School of Biosciences > Protein Science Group
Depositing User: Mark Howard
Date Deposited: 30 Sep 2008 18:41
Last Modified: 27 Jun 2014 13:47
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