Cell wall-active antibiotic induced proteins of Staphylococcus aureus identified using a proteomic approach

Abstract

Proteins produced in elevated amounts in response to oxacillin challenge of Staphylococcus aureus strain RN450, were studied by comparing Coomassie blue stained two-dimensional gels of cellular proteins. At least nine proteins were produced in elevated amounts following exposure to growth inhibitory concentrations of oxacillin. N-terminal sequences were obtained for five of the proteins and the databases were searched to tentatively identify them. The proteins were identified as homologs of (i) methionine sulfoxide reductase (MsrA) ; (ii) a signal transduction protein (TRAP) involved in regulating RNAIII production encoded by the agr locus; (iii) transcription elongation factor GreA; (iv) the heat shock protein GroES; and (v) the enzyme IIA component of the phosphoenolpyruvate:sugar phosphotransferase system. A similar induction response was observed with the other cell wall-active antibiotics, but not with antibiotics that affect other cellular targets. Increased transcription of the msrA and groEL genes in response to cell wall-active antibiotics was also demonstrated. Although net protein synthesis is inhibited subsequent to inhibition of peptidoglycan biosynthesis by cell wall-active antibiotics, some proteins are induced in S. aureus, presumably in an attempt by the cell to counter the inhibitory effects of these agents. ß

Staphylococcus aureus Strain Newman Photoinactivation and Cellular Response to Sunlight Exposure

“…The increase in msrA expression observed here under the oxic condition indicates that S. aureus cells may be responding to protein damage caused by methionine oxidation during sunlight exposure and that msrA is more important in this case than other oxidative stress response genes like sodA or trxB. Studies have also found that MsrA1 activity in S. aureus is associated with exposure to cell wall-active antibiotics (50,55), suggesting the importance of MsrA in responding to cell wall stress. As msrA expression was also increased during sunlight exposure under the anoxic condition, this may be in response to the cell membrane damage that was observed by increasing membrane permeability, indicating that the photoinactivation mechanisms acting under the anoxic condition may target cell membranes through the breakdown of membrane proteins.…”

Role for dnaK locus in tolerance of multiple stresses in Staphylococcus aureus

“…Growth was then followed by measurement of OD 600 spectrophotometrically. These stress conditions were chosen based on prior studies (Singh & Moskovitz, 2003;Singh et al, 2001aSingh et al, , 2001bUtaida et al, 2003), or on pilot studies where significant growth inhibition was observed for wild-type bacteria.…”

“…Additionally, sera from endocarditis patients have antibodies against these Hsps (Qoronfleh et al, 1993). These Hsps have also assumed significance in antibiotic action, as they are induced under cell-wall-active antibiotic stress in S. aureus (Singh et al, 2001a;Utaida et al, 2003).…”

What makes resistance to methicillin heterogeneous?

“…Twodimensional protein gels yield a type of snapshot of the state of different strains. There has so far been one study that analysed the proteins induced by cell-wallactive antibiotics (Singh et al, 2001). With the data gained in such experiments, along with increasing knowledge about the activities of global regulatory networks, it should be possible to finally pinpoint the trigger that enables the segregation of highly methicillin-resistant subclones on selection with methicillin.…”