Solubilization and electrophoretic analysis of Staphylococcus aureus membrane proteins.

The protein composition of homogeneous Staphylococcus aureus 6538P cytoplasmic membranes was examined under denaturing electrophoretic conditions. A comparative analysis on the effectiveness of a variety of membrane solubilizing agents revealed the membrane protein extracts to be qualitatively similar as determined electrophoretically but different in the quantity of protein released; Zwittergent-314, sodium dodecyl sulfate, Triton X-100, Nonidet P-40, and sodium deoxycholate all proved to be effective solubilizing agents under the conditions examined. Fifty-five to sixty protein components were resolved by sodium dodecyl sulfate polyacrylamide gel electrophoresis from homogeneous late-exponential phase membranes. The profile was unaffected when phenylmethylsulfonyl fluoride was included during membrane isolation and solubilization. Analysis of the solubilized membrane proteins by two-dimensional gel electrophoresis demonstrated in excess of 100 membrane protein components in a pH gradient between 3.5 to 7.7. The profile consisted of a heterogeneous mixture of mostly acidic components with isoelectric points between pH 4 and 5 and relative molecular weights between 158,000 and 35,000. Periodic acid-Schiff staining following sodium dodecyl sulfate gel electrophoresis revealed six to ten reactive bands with two of these bands also exhibiting a reaction with concanavalin A.