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 μ-chain had a slower mobility than did μ-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.