Fe2+ oxidation of alpha-crystallin produces a 43,000 Da aggregate composed of A and B chains cross-linked by non-reducible covalent bonds.
The structure of a 43,000 Da aggregate generated from bovine lens alpha-crystallin polypeptides of 20,000 Da using Fe2+ catalyzed oxidation, was studied by sequence analysis of a 30,000 Da proteolytic fragment. Three polypeptide components were simultaneously sequenced in the electroblotted 30,000 Da fragment, corresponding to Phe114-Ser130... of the alpha A chain, and His 111-Ser135... and Ser 35-Leu49... of the alpha B chain. The relative proportions of the components suggests that the three polypeptides are present in equimolar amounts. It is concluded that the 30,000 Da fragment and, therefore, the 43,000 Da aggregate is constructed of both the A and B polypeptide chains covalently cross-linked with non-reducible bonds. At least one of these cross-links is present towards the carboxy-terminus of the A and B chains after Phe114 and His111, respectively.
McDermott
M J
MJ
Department of Ophthalmology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Chiesa
R
R
Spector
A
A
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003432:Cross-Linking Reagents; D003459:Crystallins / Q000032:analysis; D005296:Ferrous Compounds; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction
D003432:Cross-Linking Reagents; D003459:Crystallins; D005296:Ferrous Compounds