A Sequence Restriction in the Variable Region of Immunoglobulin Light Chains from Sharks, Birds, and Mammals

A relatively conserved pentapeptide sequence is present in the variable region of normal immunoglobulin λ- and κ-chains from animals as diverse as sharks, birds, and mammals. This same conserved sequence is also present in most myeloma light chains from dog, mouse, and man. The conservation of this pentapeptide sequence over the more than 400 million years since sharks and mammals diverged suggests that this region must carry out a very important, but as yet unknown function. A homologous but less highly conserved stretch of sequence is present in the variable region of immunoglobulin heavy chains.