Mouse immunoglobulin kappa chain MPC 11: extra amino-terminal residues

The kappa chain from the immunoglobulin of myeloma tumor MPC 11 has 12 extra residues at its amino terminus, the first six of which are identical to the residues at positions 1 to 6 of typical mouse kappa chains and at positionss 13 to 18 of MPC 11 itself. Two of the peptide bonds within this extra 12-residue segment are cleaved under very mild conditions.