PDBsum entry 1c1f

Sugar binding protein

PDB id: 1c1f

Contents

Protein chain

135 a.a. *

Waters ×81

* Residue conservation analysis

PDB id:

1c1f

Name:

Sugar binding protein

Title:

Ligand-free congerin i

Structure:

Protein (congerin i). Chain: a. Fragment: carbohydrate-recognition-domain

Source:

Conger myriaster. Whitespotted conger. Organism_taxid: 7943. Tissue: skin mucus. Secretion: non-classical

Biol. unit:

Homo-Dimer (from PDB file)

Resolution:

1.60Å R-factor: 0.201 R-free: 0.247

Authors:

T.Shirai,C.Mitsuyama,Y.Niwa,Y.Matsui,H.Hotta,T.Yamane,H.Kamiya, C.Ishii,T.Ogawa,K.Muramoto

Key ref:

T.Shirai et al. (1999). 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. Structure, 7, 1223-1233. PubMed id: 10545323 DOI: 10.1016/S0969-2126(00)80056-8

Date:

03-Mar-99 Release date: 08-Oct-99

Protein chain

P26788  (LEG1_CONMY) -  Congerin-1 from Conger myriaster

Seq: 135 a.a.

Struc: 135 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1016/S0969-2126(00)80056-8

Structure 7:1223-1233 (1999)

PubMed id: 10545323

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.

T.Shirai, C.Mitsuyama, Y.Niwa, Y.Matsui, H.Hotta, T.Yamane, H.Kamiya, C.Ishii, T.Ogawa, K.Muramoto.

ABSTRACT

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.

Selected figure(s)

Figure 6.
Figure 6. Stereo pairs of omit maps around carbohydrate-binding clefts of (a) the lactoseliganded form and (b) the ligand-free form of congerin I. The lactose molecule or the water molecules in the cleft of the ligand-free form were excluded from phase calculation. The omitted atoms are shown in red, and the others are shown in blue. Both electron-density maps (green) are contoured at the 3.5s level. Glc is glucose and Gal is galactose.

The above figure is reprinted by permission from Cell Press: Structure (1999, 7, 1223-1233) copyright 1999.

Figure was selected by an automated process.