Molecular basis for the temperature-dependent insolubility of cryoglobulins. XII. Anomalous mobility of monoclonal cryoimmunoglobulin heavy chains accompanying polyacrylamide gel electrophoresis in sodium dodecyl sulfate.

When subjected to polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS), the fully reduced and alkylated heavy chains isolated from three monoclonal IgG1 cryoimmunoglobulins exhibited various degrees of retardation in mobility when compared to noncryoglobulin references. The anomalous electrophoretic mobility was not correlated with the thermal magnitude of cryoprecipitation of the individual proteins. High sensitivity analytical gel filtration in 5 M guanidine-HCl failed to distinguish heavy chains of the cryoimmunoglobulins from noncryoglobulin references, suggesting that the proteins possess equivalent molecular weights. Other possible causes for the anomalous mobility such as atypical amino acid and carbohydrate composition, charge and quantitative SDS binding do not appear to be likely. It remains possible that the shape and/or charge of the SDS-protein complexes are unique. Examination of the gel electrophoretic mobility in SDS of fully reduced and alkylated Fab components suggests that the Fd portion of these proteins may be abnormal. The gel electrophoresis anomaly is the only atypical structural feature thus detected which is shared by these three monoclonal cryoimmunoglobulins.