1c1f

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LIGAND-FREE CONGERIN I

Overview

BACKGROUND: Congerin I is a member of the galectin (animal, beta-galactoside-binding lectin) family and is found in the skin mucus of, conger eel. The galectin family proteins perform a variety of biological, activities. Because of its histological localization and activity against, marine bacteria and starfish embryos, congerin I is thought to take part, in the eels' biological defense system against parasites. RESULTS: The, crystal structure of congerin I has been determined in both, lactose-liganded and ligand-free forms to 1. 5 A and 1.6 A resolution, respectively. The protein is a homodimer of 15 kDa subunits. Congerin I, has a beta-sheet topology that is markedly different from those of known, relatives. One of the beta-strands is exchanged between two identical, subunits. This strand swap might increase the dimer stability. Of the, known galectin complexes, congerin I forms the most extensive interaction, with lactose molecules. Most of these interactions are substituted by, similar interactions with water molecules, including a pi-electron, hydrogen bond, in the ligand-free form. This observation indicates an, increased affinity of congerin I for the ligand. CONCLUSIONS: The genes, for congerin I and an isoform, congerin II, are known to have evolved, under positive selection pressure. The strand swap and the modification in, the carbohydrate-binding site might enhance the cross-linking activity, and should be the most apparent consequence of positive selection. The, protein has been adapted to functioning in skin mucus that is in direct, contact with surrounding environments by an enhancement in cross-linking, activity. The structure of congerin I demonstrates the emergence of a new, structure class by accelerated evolution under selection pressure.

About this Structure

1C1F is a Single protein structure of sequence from Conger myriaster. Full crystallographic information is available from OCA.

Reference

High-resolution structure of the conger eel galectin, congerin I, in lactose-liganded and ligand-free forms: emergence of a new structure class by accelerated evolution., Shirai T, Mitsuyama C, Niwa Y, Matsui Y, Hotta H, Yamane T, Kamiya H, Ishii C, Ogawa T, Muramoto K, Structure. 1999 Oct 15;7(10):1223-33. PMID:10545323

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