Initiation of Protein Synthesis at an Unusual Position in an Immunoglobulin Gene?

Abstract
The amino acid sequence of urinary β2-microglobulin has been partially determined and found to be related to the constant region of IgG immunoglobulin heavy chain. β2-Microglobulin is present in normal individuals. Its gene may have evolved from an immunoglobulin gene by the use of an unusually located start signal for initiating synthesis of the polypeptide.