Different species of messenger RNA encode receptor and secretory IgM μ chains differing at their carboxy termini

Abstract

Biosynthetic studies in the presence of an inhibitor of glycosylation indicate that individual human lymphoma-derived cell lines can synthesize both membrane receptor and presumptive secretory forms of Ig[immunoglobulin]M .mu. chains. The receptor form has a larger polypeptide chain than the secretory form and possesses a different C[carboxy]-terminus, but similar N-terminus, consistent with the presence of a C-terminal hydrophobic tail for integral membrane binding. Messenger RNA isolated from these cells directs the synthesis of both forms of .mu. chain in a wheat germ translation system, indicating the presence of independent mRNA for each form. The synthetic pathways for receptor and secretory IgM diverge at the posttranscriptional level, possibly by differential RNA splicing to give mRNA molecules with or without a translatable tail segment.