Structure of the Constant and 3′ Untranslated Regions of the Murine γ2b Heavy Chain Messenger RNA

The complete coding sequence for the constant region of the mouse γ2b immunoglobulin heavy chain and the 3′ untranslated region has been determined. The coding portion of the sequence is 1008 nucleotides long (amino acid residues 114 to 449), and the 3′ noncoding region contains 102 nucleotides preceeding the polyadenylate. An extra carboxyl-terminal lysine residue which had not been observed in the γ2b or other γ subclass protein sequences occurs in the nucleotide sequence and is probably processed posttranslationally. A 17-nucleotide sequence occurs with slight variation twice in C H 1 and once in C H 2 domains in the same relative location but with different translational phase. This sequence may be the site of crossover in a γ2b ⋅ γ2a heavy chain variant, an indication of possible recombinational activity of some kind.