Proteome analysis of membrane and cell wall associated proteins from Staphylococcus aureus

Pathogenesis of Staphylococcus aureus, an opportunistic human pathogen, is complex and involves many virulence factors including an array of surface proteins (adhesins) that promote bacterial interactions with extracellular matrix components. A better understanding of these interactions can be achieved by studying the expression of membrane and cell wall associated proteins using a proteome analysis approach. To accomplish this, our goal here was to construct a reference map of membrane and cell wall associated proteins for S. aureus. Various lytic and solubilization methods have been tested to identify a suitable methodology for detection of these proteins in two-dimensional electrophoresis (2DE). Results demonstrate that cell lysis with lysostaphin, which lyses staphylococcal peptidoglycan, followed by solubilization with urea, thiourea, amidosulfobetaine 14 (ASB 14) and dithiothreitol (DTT) is an effective method, yielding a sample comprising proteins of wide molecular ranges and isoelectric points with minimum contamination from cytosolic proteins. Mass spectrometric analysis was employed to identify the membrane and cell surface proteins present in the sample and consequently an initial proteomic map of membrane and cell wall associated proteins for S. aureus is presented.