Partial amino acid sequences of ?-chains of rat immunoglobulins: Genetic and evolutionary implications

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Abstract
Partial amino acid sequences have been determined for several κ-type light chains prepared from sera or urine of inbred LOU/C/Wsl rats bearing plasma cell tumors. Comparison of these sequences with those of human, rabbit, and mouse κ-chains available in the literature indicates that the constant region of rat κ-chains shows more amino acid sequence homology to that of the mouse κ-chain than to human and rabbit κ-chains, a result expected from the phylogenetic relationship of the species compared. Examination of the N-terminal amino acid sequences indicated that the variable regions of rat κ-chains can also be classified into subgroups according to degree of sequence homology in a manner similar to that done for κ-chains of other species (e.g., human, rabbit, and mouse). However, the prototype amino acid sequences of κ-chain variable region subgroups of the rat were not homologous to those of other species including the closely related mouse. The implications of this observation with respect to the genetics and evolution of immunoglobulins are discussed.