Complementary Analysis of the Vegetative Membrane Proteome of the Human Pathogen Staphylococcus aureus*□S

The Gram-positive bacterium Staphylococcus aureus is a serious human pathogen causing a wide variety of dis-eases, and its increasing resistance toward all available antibiotics makes its further investigation absolutely es-sential. We examined the membrane proteome of expo-nentially growing cells of S. aureus COL because this subproteome plays a major role in the virulence of the bacterium in its host. In general, an analysis of membrane proteins is impeded by their hydrophobic nature as well as by a high abundance of many cytosolic proteins. The implementation of three different technologies, one-di-mensional gel-LC, two-dimensional LC, and a membrane shaving approach combined with MS/MS analyses, en-abled an identification of 271 integral and 86 peripheral membrane proteins from exponentially growing cells. In particular, the latter approach that combined membrane shaving with a subsequent chymotrypsin digest of inte-gral membrane domains of proteins greatly facilitated the detection of hydrophobic peptides derived from mem-brane-spanning segments (713 peptides, 60 % of all pep-tides) and therefore yielded almost exclusively highly hydrophobic integral membrane proteins (96.7%). A comparison of the various methods disclosed the one-dimensional gel-LC and the shaving approach to be highly complementary techniques. A combination of them will reveal a most comprehensive view on membrane proteomes. Molecular & Cellular Proteomics 7