Immunochemical Properties of Vertebrate α‐Crystallins

Abstract

A competitive radioimmunoassay was used to determine the reactivities of α‐crystallins from 13 species with antibodies directed toward calf α‐crystallin. The results indicate that species as diverse as human and dogfish share the same number of crossreacting antigenic determinants. The various α‐crystallins can be distinguished only on the basis of their differing affinities for the antiserum. Hydrophilicity profiles for αA and αB polypeptides of all species were found to be remarkably similar. On the basis of these, four major sequential determinants could be predicted for each polypeptide. The location and sequence of these determinants were found to be essentially conserved in all α‐crystallins examined. These results are in agreement with the observed crossreactivities. However, there was little obvious correlation between substitutions in determinants and observed variations in respective α‐crystallin/antibody affinities. Conservation of antigenic determinants over such a wide evolutionary range may reflect stringent constraints on the overall surface and three‐dimensional structure of vertebrate α‐crystallins.