Subsystem: Adhesins in Staphylococcus
This subsystem's description is:
For more information, please check out the description and the additional notes tabs, below
|Diagram||Functional Roles||Subsystem Spreadsheet||Additional Notes|
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1 = a set of adhesins in S. aureus
2 = a set of adhesins in S. epidermidis
3 = in other Staphylococcus species
Staphylococcus aureus can adhere to components of the extracellular matrix (ECM) and plasma of the host to initiate colonization. Adherence is mediated by:
(i) protein adhesins of the MSCRAMM family (Microbial Surface Components Recognizing Adhesive Matrix Molecules), which in most cases are covalently anchored to the cell wall peptidoglycan;
(ii) extracellular secreted proteins capable of binding various host plasma and ECM components such as fibrinogen, von Willebrand factor, bone sialoprotein and others;
(iii) extracellular polysaccharide termed ‘poly-N-acetylglucosamine (PNAG)’ in S. aureus and ‘polysaccharide intercellular adhesin (PIA)’ in S. epidermidis.
I. Cell-wall-anchored MSCRAMMs have recognizable structure. A long (~40 amino acids) N-terminal signal sequence is required for Sec-dependent protein secretion. It is followed by a nonrepetitive domain, largely responsible for ligand binding. It is followed in turn by a repetitive domains consisting of either long (38-137 aa) repetitive elements, or/and an extended series of Serine-Aspartate (SD) dipeptide repeats. The C-terminal region (wall-spanning domain –> membrane-spanning domain –> (+) charged cytoplasmic anchor) constitutes a sorting signal, which facilitates incorporation of MSCRAMMs into S. aureus cell wall. The hallmark of the sorting signal is an LPXTG motif. The LPXTG motif is cleaved between the Thr and Gly residues by transpeptidase sortase and the carboxyl group of Thr is covalently joined to the carboxyl group of a branch peptide in the peptidoglycan. In the case of S. aureus, this is a pentaglycine sequence.
Many characterized members of this family are described in detail in the database of Virulence Factors of Pathogenic Bacteria at: http://www.mgc.ac.cn/cgi-bin/VFs/genus.cgi?Genus=Staphylococcus
In addition to well studied MSCRAMMs, several hypothetical S.aureus proteins with a LPXTG (or LPXaG) motif and similar domain architecture (hence, cell-surface-anchored) have been included in this SS (based on Roche et al., 2003). Although their function is not clear yet, two of them (SasG and SasH) have been significantly associated with in invasive disease isolates (as compared to carriage isolates from healthy donors (Roche et al., 2003)). These are grouped under the "*Hyp_surface_proteins" subset of roles. Please click "ignore alternatives" check-box to view in detail
II. Although the role of extracellular binding proteins in Staph infections have been established, it is not necessarily adhesion to host tissues. For instance, Efb is believed to bind soluble fibrinigen in a manner that delays clot formation and hence delays wound healing (Palma et al., 1996); Eab promotes S. aureus aggregation and enhances internalization into eukaryotic cells (Haggar et al., 2003). For a review see (1).
III. In addition to the protein adhesins, the icaABCD operon (for intercellular adhesion (Heilmann et al., 1996)), encoding the biosynthesis of polysaccharide intercellular adhesin (PIA) is important for adhesion (it is NOT included in this Subsystem, see SS: Biofilm formation in Staphylococcus). PIA is a partially N-acetylated linear beta-1–6-linked glucosaminoglycan. It is essential for the second step of biofilm formation - intercellular adhesion or growth-dependent multilayered cell cluster accumulation (the first step being an attachment of bacterial cells to a polymer surface). PIA is also involved in haemagglutination and acts as an intercellular adhesin on glass and (probably) other hydrophilic surfaces (refs. 5-8)
1. M. Smeltzer “Characterization of Staphylococcal adhesions for adherence to host tissues”. In: Handbook of Bacterial Adhesion: Principles, Methods, and Applications (Y.H. An, R.J. Friedman, eds.), 2000, Humana Press, Totowa, NJ
2. Haggar A, Hussain M, Lonnies H, Herrmann M, Norrby-Teglund A, Flock JI. 2003. Extracellular adherence protein from Staphylococcus aureus enhances internalization into eukaryotic cells. Infect Immun. 71(5):2310-7
3. Tung H, Guss B, Hellman U, Persson L, Rubin K, Ryden C. 2000. A bone sialoprotein-binding protein from Staphylococcus aureus: a member of the staphylococcal Sdr family. Biochem J, 345(3):611-9.
4. Roche, F. M., Massey, R., Peacock, S. J., Day, N. P. J., Visai, L., Speziale, P., Lam, A., Pallen, M. & Foster, T. J. (2003). Characterization of novel LPXTG-containing proteins of Staphylococcus aureus identified from genome sequences. Microbiology 149, 643–654
5. Hartleib J, Kohler N, Dickinson RB, Chhatwal GS, Sixma JJ, Hartford OM, Foster TJ, Peters G, Kehrel BE, Herrmann M. 2000. Protein A is the von Willebrand factor binding protein on Staphylococcus aureus. Blood, 96(6):2149-56.
6. Heilmann C, et al., 1996. Molecular basis of intercellular adhesion in the biofilm-forming Staphylococcus epidermidis. Mol. Microbiol. 20(5):1083-1091.
7. McKenney D, et al., 1998. The ica locus of Staphylococcus epidermidis encodes production of the capsular polysaccharide/adhesin. Infect. Immun. 66(10):4711-4720.
8. Cramton SE, et al., 1999. The intercellular adhesion (ica) locus is present in Staphylococcus aureus and is required for biofilm formation. Infect. Immun. 67(10):5427-5433.