title: Physicochemical characterization of a crystallin from the squid lens and its comparison with vertebrate lens crystallins.
abstract: A crystallin was isolated from the homogenate of the Squid (Loligo pealii) lens by gel filtration on a Sepharose CL-6B (2.5 X 170 cm) column. Biochemical characterization showed it is a dimeric protein with a molecular weight of (5.1 +/- 0.4) X 10(4) and a Stokes' radius of 26A. Electrophoresis on a cellulose acetate membrane indicated it is a basic protein with an isoelectric point higher than 8.6. High resolution two-dimensional gel in 8 M urea/2% NP-40 resolved this crystallin into 6 charge isomers, each with a major subunit of molecular weight 29,000 daltons and a minor subunit of 27,000 daltons in a molar ratio of 3:1. The extreme susceptibility of the protein to denaturation and precipitation even at low temperature hampered further characterization of this crystallin under nondenaturing conditions. Amino acid analysis indicated it contains an unusually high content of methionine (12.8 mol%) which may have some bearing on the instability of this crystallin in vitro. Biochemical comparison of the squid crystallin with mammalian lens crystallins shows that it is a crystallin distinguishable from all reported vertebrate lens crystallins. A detailed study of this protein may shed light on the evolution of lens crystallins in general.
mesh_terms: D000596:Amino Acids / Q000302:isolation & purification; D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D002627:Chemistry, Physical; D002847:Chromatography, Agarose; D003459:Crystallins / Q000302:isolation & purification*; D049832:Decapodiformes / Q000032:analysis*; D004586:Electrophoresis / Q000379:methods; D005399:Fishes; D013045:Species Specificity
chemical_list: D000596:Amino Acids; D003459:Crystallins