Primary Structures of the α-Crystallin A Chains of Seven Mammalian Species.

The sequence determination of the aA chains of α-crystallin from pig, horse, dog, cat, rabbit, rat and rhesus monkey is described. Most residues were placed by homology with the known bovine sequence, after amino acid analyses of tryptic and thermolytic peptides. Sequences were established, using the dansyl-Edman method, whenever peptides differed in composition from the homologous bovine peptides. The number of observed amino acid replacements among these mammalian αA chains is relatively small, but the rate at which substitutions have occurred varies greatly between the different evolutionary lineages. The amino acid replacements are not randomly distributed along the aA chain, most substitutions occurring in the C-terminal part of the chain. The rabbit, rat and monkey αA chains have four substitutions in common, indicating a polygenetic relationship between these species. [ABSTRACT FROM AUTHOR]