Extracellular proteins ofStaphylococcus aureus and the role of SarA andσB

Abstract

Staphylococcus aureus synthesizes a large number of extracellular proteins that have been postulated to play a role in bacterial virulence. The proteomic approach was used to analyse the pattern of extracellular proteins of two different S. aureus strains, RN6390 and COL. Thirty-nine protein spots were identified by N-terminal sequencing or MALDI-TOF-MS. The differences of the extracellular protein patterns between both strains are striking. Among the 18 proteins identified in S. aureus COL there are nine proteins not yet discovered in S. aureus RN6390. These are enterotoxin B, leukotoxin D, enterotoxin, serin proteases (SplA and SplC), thermonuclease, an IgG binding protein and two so far unknown proteins in S. aureus with similarities to SceD precursor in Staphylococcus carnosus and to synergohymenotropic toxin precursor in Streptococcus intermedius. In contrast, lipase as well as staphylokinase identified in S. aureus RN6390 were not detectable in S. aureus COL under the same conditions. By using a regulatory mutant of sarA (ALC136) isogenic to strain RN6390 we identified five proteins positively regulated by SarA and 12 proteins negatively regulated by SarA. Besides V8 protease (StsP) and Hlb already described to be regulated by the sar locus new putatively sarA-dependent proteins were identified, e.g. glycerolester hydrolase and autolysin both down-regulated in the sarA mutant, and aureolysin, staphylokinase, staphopain and format tetrahydrofolate lyase up-regulated in the mutant. Moreover, the role of sigma B in expression of extracellular proteins was studied. Interestingly, we found 11 proteins at an enhanced level in a sigB mutant of S. aureus COL, among them enterotoxin B, alpha and beta hemolysin, serine proteases SplA and SplB, leukotoxin D, and staphopain homologues. The sigma B-dependent repression of gene expression occurs at the transcriptional level. Only one protein, SceD, was identified whose synthesis was down-regulated in the mutant indicating that its gene belongs to the sigma B-dependent general stress regulon.

The extracellular and cytoplasmic proteomes of the non-virulentBacillus anthracis strain UM23C1-2

“…We observed the presence of two sulfatases (BA2947 and BA5470) in the extracellular proteome of B. anthracis that were also identified as their homologous proteins YfnI and YflE in the extracellular proteomes of B. subtilis, Staphylococcus aureus and B. licheniformis ( [12,33] and B. Voigt, and M. Hecker, unpublished data). YfnI/YflE homologues are polytopic transmembrane proteins in which cleavage sites are located in the C-terminus of the fifth transmembrane domain [34].…”

The secretome ofPleurotus sapidus

“…Since immobilized pH-gradient strips allow for reproducible electrophoretic separation conditions, 2-DE has become the method of choice for biochemical secretome analysis. Detailed investigations have been performed so far either on microorganisms of outstanding biotechnological importance, such as Saccharomyces cerevisiae and the Gram-positive bacterium Bacillus subtilis [19], or on pathogenic species like Bacillus cereus [20], Bacillus anthracis [21], Clostridium difficile [22], and Staphylococcus aureus [23,24]. Completed genome projects on these organisms permit a fast identification of protein spots on the basis of their peptide mass fingerprints, generated by tryptic in-gel digestion and automated MALDI-MS in high-throughput platforms.…”

Opposing roles of σB and σB-controlled SpoVG in the global regulation of esxA in Staphylococcus aureus

“…RNAIII transcription is enhanced by the staphylococcal accessory regulator SarA [2] and reduced by the alternative sigma factor σ B in strain Newman [3,4]. SarA is a winged helix transcription factor influencing many virulence genes [5,6]. The transcription of sarA in turn is directly activated by the alternative sigma factor σ B [3], which controls over 250 genes including virulence factors and secondary regulators in a direct or indirect way [7].…”