1M26

Crystal structure of jacalin-T-antigen complex

Summary for 1M26

• Entry DOI: 10.2210/pdb1m26/pdb
• Related: 1JAC
• Related PRD ID: PRD_900084
• Descriptor: Jacalin, alpha chain, Jacalin, beta chain, beta-D-galactopyranose-(1-3)-2-acetamido-2-deoxy-alpha-D-galactopyranose, ... (4 entities in total)
• Functional Keywords: all beta sheet protein, beta prism i fold, sugar binding protein, plant protein
• Biological source: Artocarpus integer; More
• Total number of polymer chains: 8
• Total formula weight: 66862.81

Authors

Jeyaprakash, A.A.,Rani, P.G.,Reddy, G.B.,Banumathi, S.,Betzel, C.,Surolia, A.,Vijayan, M. (deposition date: 2002-06-21, release date: 2002-10-12, Last modification date: 2024-02-14)

Primary citation

Jeyaprakash, A.A.,Rani, P.G.,Reddy, G.B.,Banumathi, S.,Betzel, C.,Surolia, A.,Vijayan, M.
Crystal structure of the jacalin-T-antigen complex and a comparative study of lectin-T-antigen complexs
J.Mol.Biol., 321:637-645, 2002

PubMed Abstract: Thomsen-Friedenreich antigen (Galbeta1-3GalNAc), generally known as T-antigen, is expressed in more than 85% of human carcinomas. Therefore, proteins which specifically bind T-antigen have potential diagnostic value. Jacalin, a lectin from jack fruit (Artocarpus integrifolia) seeds, is a tetramer of molecular mass 66kDa. It is one of the very few proteins which are known to bind T-antigen. The crystal structure of the jacalin-T-antigen complex has been determined at 1.62A resolution. The interactions of the disaccharide at the binding site are predominantly through the GalNAc moiety, with Gal interacting only through water molecules. They include a hydrogen bond between the anomeric oxygen of GalNAc and the pi electrons of an aromatic side-chain. Several intermolecular interactions involving the bound carbohydrate contribute to the stability of the crystal structure. The present structure, along with that of the Me-alpha-Gal complex, provides a reasonable qualitative explanation for the known affinities of jacalin to different carbohydrate ligands and a plausible model of the binding of the lectin to T-antigen O-linked to seryl or threonyl residues. Including the present one, the structures of five lectin-T-antigen complexes are available. GalNAc occupies the primary binding site in three of them, while Gal occupies the site in two. The choice appears to be related to the ability of the lectin to bind sialylated sugars. In either case, most of the lectin-disaccharide interactions are at the primary binding site. The conformation of T-antigen in the five complexes is nearly the same.

PubMed: 12206779
DOI: 10.1016/S0022-2836(02)00674-5

Experimental method

X-RAY DIFFRACTION (1.62 Å)