Cardiac sarcoplasmic reticulum and sarcolemmal proteins separated by two‐dimensional electrophoresis: Surfactant effects on membrane solubilization

We evaluated the use of the alkyaryl amidosulfobetaine zwitterionic detergent, designated as C8psi, to facilitate the solubilization of cardiac subcellular, membrane-associated proteins. Hearts from 7-week-old male Sprague-Dawley rats were isolated, and the left ventricles dissected and subsequently homogenized. The sarcolemma (SL) and the sarcoplasmic reticulum (SR) were isolated from different homogenate preparations originating from rat hearts by ultracentrifugation methods. The isolated membrane preparations were solubilized and the proteins precipitated. After resuspension, protein separation was achieved in first-dimensional IEF using an immobilized (pH 4-7) gradient and in the second dimension using 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Gels were then stained, images analyzed, and protein spots excised for subsequent identification. Protein identification from both SR and SL samples did not identify any of the known major membrane-associated proteins. Solubilization of whole tissue lysates with C8psi resulted in no increase in the total number of proteins detected relative to samples solubilized in the presence of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulforate (CHAPS). The data suggest the utility of newer surfactants such as C8psi to improve both the resolution of (2-D) protein profiles and increase the number of proteins extracted from subcellular organelle fractions.