Structure of the glycopeptides of a human γ1-immunoglobulin G (Tem) myeloma protein as determined by 360-megahertz nuclear magnetic resonance spectroscopy

High field magnetic resonance spectroscopy has been utilized to deduce the primary structure of the glycopeptides from a human myeloma γ1-immunoglobulin G (Tem). The major structures found belong to the biantennary complex class of glycopeptides, with a minor (5%) fraction belonging to the bisected biantennary complex class. In the biantennary class, three structures were present with different residues at the termini of the αMan(1-6) and αMan(1-3) arms: (i) with βGal(1-4) and αNeuNAc(2-6), respectively (33%); (ii) with βGal(1-4) and βGal(1-4), respectively (45%); and (iii) βGal(1-4) and βGlcNAc(1-2), respectively (17%). In the bisected biantennary class only the latter termini were found for the two arms. These results suggest that the galactosyl transferase in these cells has a preference for the βGlcNAc(1-2) of the αMan(1-6) arm and that the sialyltransferase has a preference for the βGal(1-4) of the αMan(1-3) arm.