3bc6

From Proteopedia

Revision as of 09:18, 23 January 2008

The carbohydrate recognition domain of Langerin reveals high structural similarity with the one of DC-SIGN but an additional, calcium-independent sugar-binding site

Overview

Langerin is a type II transmembrane oligosaccharide receptor on Langerhans, cells (LCs), a prominent subclass of dendritic cells (DCs) that mediate, immune responses in epithelia and play a role in HIV degradation. Its, extracellular moiety comprises a neck region with several heptad repeats, and an exposed carboxy-terminal calcium-type carbohydrate-recognition, domain (CRD). The CRD of human Langerin, which was expressed as a soluble, protein in the periplasm of E. coli, was crystallized both alone and in, the presence of two sugars, followed by X-ray analyses to resolutions of, 2.5A for apo-Langerin and to 1.6A and 2.1A for the complexes with mannose, and maltose, respectively. The fold of the Langerin CRD (dubbed LangA), resembles that of other typical C-type lectins such as DC-SIGN. However, especially in the long loop region (LLR), which is responsible for, carbohydrate-binding, two additional secondary structure elements are, present: a 3(10) helix and a small beta-sheet arising from the extended, beta-strand 2, which enters into a hairpin and a new strand beta2'., Unexpectedly, the crystal structures in the presence of maltose and, mannose reveal two sugar-binding sites. One is calcium-dependent and, structurally conserved in the C-type lectin family whereas the second one, represents a novel, calcium-independent type. Based on these data, a model, for the binding of mannan, a component of many endogenous as well as viral, glycoproteins, is proposed and the differences in binding behavior between, Langerin and DC-SIGN with respect to the Lewis X carbohydrate antigen and, its derivatives can be explained. Therefore, the crystal structure of, LangA should be helpful for the development of new marker reagents, selective for LCs and also of therapeutic compounds that may enhance the, inhibitory role of Langerin towards HIV infection.

About this Structure

3BC6 is a Single protein structure of sequence from Homo sapiens with and as ligands. Full crystallographic information is available from OCA.

Reference

The carbohydrate recognition domain of Langerin reveals high structural similarity with the one of DC-SIGN but an additional, calcium-independent sugar-binding site., Chatwell L, Holla A, Kaufer BB, Skerra A, Mol Immunol. 2007 Nov 30;. PMID:18061677

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