Identification of surface proteins in Enterococcus faecalis V583

Abstract

BackgroundSurface proteins are a key to a deeper understanding of the behaviour of Gram-positive bacteria interacting with the human gastro-intestinal tract. Such proteins contribute to cell wall synthesis and maintenance and are important for interactions between the bacterial cell and the human host. Since they are exposed and may play roles in pathogenicity, surface proteins are interesting targets for drug design.ResultsUsing methods based on proteolytic "shaving" of bacterial cells and subsequent mass spectrometry-based protein identification, we have identified surface-located proteins in Enterococcus faecalis V583. In total 69 unique proteins were identified, few of which have been identified and characterized previously. 33 of these proteins are predicted to be cytoplasmic, whereas the other 36 are predicted to have surface locations (31) or to be secreted (5). Lipid-anchored proteins were the most dominant among the identified surface proteins. The seemingly most abundant surface proteins included a membrane protein with a potentially shedded extracellular sulfatase domain that could act on the sulfate groups in mucin and a lipid-anchored fumarate reductase that could contribute to generation of reactive oxygen species.ConclusionsThe present proteome analysis gives an experimental impression of the protein landscape on the cell surface of the pathogenic bacterium E. faecalis. The 36 identified secreted (5) and surface (31) proteins included several proteins involved in cell wall synthesis, pheromone-regulated processes, and transport of solutes, as well as proteins with unknown function. These proteins stand out as interesting targets for further investigation of the interaction between E. faecalis and its environment.

Cold-shock RNA-binding protein CspR is also exposed to the surface of Enterococcus faecalis

“…Bøhle et al (2011) identified 69 surface proteins of E. faecalis, including CspR (EF2925), which supported our findings. As this was unexpected, we verified the extracellular location of CspR by different approaches such as Western blotting, identification of surface polypeptides by proteolytic shaving of intact bacterial cells and immunolocalization.…”

“…This hypothesis was also supported by the presence of CspR (EF2925) among the surface proteins identified by Bøhle et al (2011). Thus, detection of CspR on the total cytoplasmic, secreted and surface protein fractions by Western immunoblotting was undertaken.…”

“…Interestingly, among them, 29 were characterized as soluble proteins (Maddalo et al, 2011). Identification of a priori cytoplasmic proteins is not unusual and it is well known that some proteins lacking signal sequences or motifs important for their secretion, such as LuxS of Salmonella (Kint et al, 2009), SodA of Listeria (Archambaud et al, 2006) or enolase of E. faecalis (Boël et al, 2004), may have an extracellular location thanks to 'non-classical secretion' (Benachour et al, 2009;Bendtsen et al, 2005;Bøhle et al, 2011). For example, the ribosomal protein L7/L12 identified on the surface of Helicobacter pylori or Brucella abortus has immunogenic properties (Mallick et al, 2007;Voland et al, 2002).…”

EF0176 and EF0177 from Enterococcus faecalis V583 are substrate-binding lipoproteins involved in ABC transporter mediated ribonucleoside uptake

“…In a recent study on the surface proteome of E. faecalis (Bøhle et al, 2011) 17 lipoproteins (of a predicted total of 74) were detected, among which were EF0176 and EF0177 that are putative SBPs of an ABC transporter encoded by the ef0176-ef0180 gene cluster (Fig. 1).…”

A Genomic Virulence Reference Map of Enterococcus faecalis Reveals an Important Contribution of Phage03-Like Elements in Nosocomial Genetic Lineages to Pathogenicity in a Caenorhabditis elegans Infection Model

“…This protein was predicted to contain a lipobox motif and is expected to be a surface-exposed element (45,63). Lipoproteins represent approximately 25% of the proteins predicted to be associated with E. faecalis cell envelope, and they are reported to be involved in substrate binding and in delivery to ABC transporters, acquisition of sugars, protein folding, antibiotic resistance, and cell envelope stability (64,65). In addition, lipoproteins play a significant role in virulence, as they mediate adhesion to the extracellular matrix (ECM), initiation of the inflammatory process followed by activation of the immune system, induction of phagosome escape, and translocation of virulence factors (63).…”