Cell surface immunoglobulin. XVI. Polypeptide chain structure of mouse IgM and IgD-like molecule.

125I-membrane IgM, 125I-membrane IgD-like molecules, and their constituent chains from iodinated murine splenocytes were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The apparent m.w. of the heavy chains decreased as the acrylamide concentration was raised. The membrane mu-chain had a slower mobility than did mu-chain from secreted IgM. Unreduced IgM and IgD-like molecules had mobilities consistent with an H2L2 structure. Intact IgD-like molecules were replaced after overnight dialysis by molecules with the properties of HL. Unreduced surface IgM had a slower mobility than that of monomeric IgM obtained by partial reduction of secreted IgM.