title: Modification of alpha-crystallin subunit chains and formation of alpha-neoprotein molecules: role of SH groups.
abstract: Immunoadsorbents with bound antibodies restricted to determinants dependent on alpha-crystallin's quaternary structure permitted the fractionation of the population of 125I-labeled alpha-crystallin molecules, treated by iodoacetic acid, into molecules in which the native structure was still preserved and molecules with a completely different quaternary structure than the native protein. Parallel experiments with [14C]iodoacetic acid yielded information on the percentage of blocked SH groups in each of the above two fractions. The presence of molecules formed by A with B-chain association was established by sequential binding first to an immunoadsorbent with antibodies restricted to determinants located on alpha-crystallin's A-subunit chains as ligand and second, after desorption, to an immunoadsorbent with antibodies to B chains as ligand. With the aid of these techniques, it was established that (i) The modified alpha-crystallin molecules with quaternary determinants of the native protein contained a maximum of 23% blocked SH groups, indicating that the carboxymethylation involved only the fast-reacting surface SH groups. (ii) The modified alpha-crystallin molecules without the native protein's quaternary structure were built by a different association between A and B subunits than in alpha-crystallin, indicating formation of alpha-neoprotein molecules. (iii) Monomeric A chains with all SH groups carboxymethylated, and monomeric B chains in a ratio of 1A:5B, 2A:1B, and 5A:1B in urea solution, associate on dialysis, forming alpha-neoprotein molecules.
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D003459:Crystallins; D007163:Immunosorbent Techniques; D046911:Macromolecular Substances; D010446:Peptide Fragments; D013438:Sulfhydryl Compounds / Q000032:analysis
chemical_list: D003459:Crystallins; D046911:Macromolecular Substances; D010446:Peptide Fragments; D013438:Sulfhydryl Compounds