Structure based studies of the adaptive diversification process of congerins

• Published in: Molecular diversity 2006-11, Vol.10 (4), p.567-573
• Main Authors: Shirai, Tsuyoshi, Shionyu-Mitsuyama, Clara, Ogawa, Tomohisa, Muramoto, Koji
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; Binding Sites; Evolution; Evolution, Molecular; Galectins - chemistry; Galectins - genetics; Ligands; Mutation; Pisces; Protein Structure, Tertiary; Proteins; Selection, Genetic; Structural Homology, Protein; Structure-Activity Relationship
• ISSN: 1381-1991; 1573-501X
• DOI: 10.1007/s11030-006-9030-8

The isoforms of a fish galectin, congerins I and II, have several features that make them suitable for a study of accelerated process of molecular diversification based on 3D structures: They have been generated by a gene duplication, and still maintain 47% amino acid sequence identity to each other. Their genes show very high K A: /K S: ratio, and are though to be components of fish defense system. The crystal systems for a high-resolution analysis are known for both proteins. A series of works with biochemistry, molecular biology, and X-ray crystallography techniques have suggested that the two proteins might have evolved under differential selection pressures. Congerin I appeared to be a stabilized version of galectin-1. Congerin II was shown to be adapted to a new carbohydrate-ligand. The 3D structures of the wild type and mutant proteins have revealed the probable cause and consequence of the selection pressure responsible for the diversification of congerins.