N-terminal sequences of immunoglobulin heavy and light chains from three species of lower vertebrates.

Abstract

IT has been established that immunoglobulin heavy (H) and light (L) chains have a variable amino terminal region of about 110–120 residues1–9. This region presumably makes up the antibody binding site and is responsible for the high degree of antigenic specificity that is a characteristic feature of these molecules. In spite of the growing body of amino-acid sequence data on immunoglobulin H and L chains, the genetic mechanisms by which an almost infinite array of specific antibodies can be expressed in response to antigenic stimulation remain to be established. It has been proposed, as one possible explanation, that the genes coding for the immunoglobulin polypeptide chains, are present in the germ line10–11. This study was prompted by this concept, as well as the structural similarities that have been demonstrated among various H and L chains, suggesting that genes coding for these chains evolved from a common ancestral gene12,13. We have investigated immunoglobulins from three lower vertebrates in the hope that sequence data of the variable region of these chains will provide an insight into the genetic mechanisms responsible for antibody variability.