ζ-Crystallin versus other members of the alcohol dehydrogenase super-family Variability as a functional characteristic

• Published in: FEBS LETTERS Vol. 322; no. 3; pp. 240 - 244
• Main Authors: Jörnvall, Hans, Persson, Bengt, Du Bois, Garrett C., Lavers, Gene C., Chen, John H., Gonzalez, Pedro, Rao, P.Vasantha, Zigler, J.Samuel
• Format: Journal Article Publication
• Language: English
• Published: Amsterdam Elsevier B.V 17.05.1993; Elsevier
• Subjects: Alcohol dehydrogenase; Alcohol Dehydrogenase - chemistry; Alcohol Dehydrogenase - metabolism; Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cattle; Conserved Sequence; Crystallin; Crystallins - chemistry; Crystallins - metabolism; Fundamental and applied biological sciences. Psychology; Glycine conservation; Guinea Pigs; Humans; Mice; Miscellaneous; Molecular Sequence Data; Proteins; Segment variability; Sequence Homology, Amino Acid; Structure-Activity Relationship; Structure—function relationship; Glycine conservation; Structure—function relationship; Crystallin; Alcohol dehydrogenase; Segment variability; Proteins; Human; Molecular evolution; Vertebrata; Mammalia; Enzyme; Structure function relationship; Aminoacid sequence
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(93)81578-N

Species variability of the lens protein ζ-crystallin was correlated with those of alcohol dehydrogenases of classes I and III and sorbitol dehydrogenase in the same protein family. The extent of overall variability, nature of residues conserved, and patterns of segment variability, all fall within the limits typical of the ‘variable’ group of medium-chain alcohol dehydrogenases. This shows that ζ-crystallin is subject to restrictions similar to those of classical liver alcohol dehydrogenase and therefore derived from a metabolically active enzyme like other enzyme crystalline. Special residues at the active site, however, differ substantially, including an apparent lack of a zinc-binding site. This is compatible with altered functional properties and makes the spread within this medium-chain dehydrogenase family resemble the wide spread within the short-chain dehydrogenases. Schematic plotting is useful for illustrating the differences between ‘variable’ and ‘constant’ enzymes.