The immunoglobulin μ chains of membrane-bound and secreted IgM molecules differ in their C-terminal segments
1980; Cell Press; Volume: 21; Issue: 2 Linguagem: Inglês
10.1016/0092-8674(80)90476-6
ISSN1097-4172
AutoresMarilyn R. Kehry, S. J. Ewald, R. Douglas, Carol Hopkins Sibley, William C. Raschke, D M Fambrough, Leroy Hood,
Tópico(s)Immune Cell Function and Interaction
ResumoThe B lymphocyte synthesizes two forms of IgM molecules during its development from a stem cell to a mature antibody-secreting plasma cell. The monomeric receptor IgM molecule is affixed to the plasma membrane and triggers the later stages of B cell differentiation, whereas the pentameric secreted IgM molecule is an effector of humoral immunity. The structural differences between membrane-bound and secreted IgM molecules are reflected in the differences between their heavy or mu chains. We have previously determined the complete amino acid sequence of a murine secreted mu (μs) chain. In this study, we have compared the structures of the secreted and membrane-bound mu (μm) heavy chains by peptide mapping, microsequence and carboxypeptidase analyses. These studies demonstrate that the μm and μs chains are very similar throughout their VH, Cμ1, Cμ2, Cμ3 and Cμ4 domains. The μm and μs chains differ in the amino acid sequence of their C-terminal segments. These studies in conjunction with those carried out on the μm and μs mRNAs and the Cμ gene suggest that the μm and μs chains from a given B cell are identical except for their 41 and 20 residue C-terminal segments, respectively. The amino acid sequence of the 41 residue C membrane terminal segment predicted from the corresponding μm mRNA is in agreement with all the protein studies reported in this paper.
Referência(s)