Surface Proteins of Gram-Positive Bacteria and Mechanisms of Their Targeting to the Cell Wall Envelope

Abstract

SUMMARY The cell wall envelope of gram-positive bacteria is a macromolecular, exoskeletal organelle that is assembled and turned over at designated sites. The cell wall also functions as a surface organelle that allows gram-positive pathogens to interact with their environment, in particular the tissues of the infected host. All of these functions require that surface proteins and enzymes be properly targeted to the cell wall envelope. Two basic mechanisms, cell wall sorting and targeting, have been identified. Cell well sorting is the covalent attachment of surface proteins to the peptidoglycan via a C-terminal sorting signal that contains a consensus LPXTG sequence. More than 100 proteins that possess cell wall-sorting signals, including the M proteins of Streptococcus pyogenes, protein A of Staphylococcus aureus, and several internalins of Listeria monocytogenes, have been identified. Cell wall targeting involves the noncovalent attachment of proteins to the cell surface via specialized binding domains. Several of these wall-binding domains appear to interact with secondary wall polymers that are associated with the peptidoglycan, for example teichoic acids and polysaccharides. Proteins that are targeted to the cell surface include muralytic enzymes such as autolysins, lysostaphin, and phage lytic enzymes. Other examples for targeted proteins are the surface S-layer proteins of bacilli and clostridia, as well as virulence factors required for the pathogenesis of L. monocytogenes (internalin B) and Streptococcus pneumoniae (PspA) infections. In this review we describe the mechanisms for both sorting and targeting of proteins to the envelope of gram-positive bacteria and review the functions of known surface proteins.

Existence and characterization of allelic variants of Sao, a newly identified surface protein fromStreptococcus suis

“…It is widely accepted that the cell-wall-exposed proteins/ outer surfaces of pathogenic bacteria are of great importance to understanding their pathogenesis (Navarre & Schneewind, 1999;Cabanes et al, 2002). Not only are surface-associated components implicated in bacterial defense machineries but also they are involved in virulencerelated behaviors (e.g., adhesion) (Navarre & Schneewind, 1999;Maione et al, 2005). Thus, for vaccine development against pathogenic bacteria, current interest has shifted from the CPS antigen to surface proteins with robust immunogenicity (Navarre & Schneewind, 1999;Cabanes et al, 2002;Maione et al, 2005;Li et al, 2006).…”

“…Not only are surface-associated components implicated in bacterial defense machineries but also they are involved in virulencerelated behaviors (e.g., adhesion) (Navarre & Schneewind, 1999;Maione et al, 2005). Thus, for vaccine development against pathogenic bacteria, current interest has shifted from the CPS antigen to surface proteins with robust immunogenicity (Navarre & Schneewind, 1999;Cabanes et al, 2002;Maione et al, 2005;Li et al, 2006). Whole genome-wide screening was carried out to search for a universal Group B Streptococcus (GBS) vaccine (Maione et al, 2005).…”

“…Whole genome-wide screening was carried out to search for a universal Group B Streptococcus (GBS) vaccine (Maione et al, 2005). These surface proteins containing a C-terminal cell wall anchoring motif (LPXTG) have been found in a variety of pathogenic microorganisms, and suggested to execute key steps during the process of infection, which range from colonization to invasion (Navarre & Schneewind, 1999;Cabanes et al, 2002;Osaki et al, 2002;Maione et al, 2005). In S. suis, MRP belongs to this type of surface protein (Smith et al, 1992).…”

Simultaneous Extraction of Viral and Bacterial Nucleic Acids for Molecular Diagnostic Applications

“…Enzymatic treatment with lysozyme has also been shown effective in lysing certain gram-positive species. 21,22 Upon lysozyme treatment, H. influenzae and S. aureus were detected across a range of concentrations of starting material ( Table 1). Whereas the S. aureus genome copy numbers being detected in the PLEX-ID platform were generally lower compared with H. influenzae, detection of the former organism was significantly improved after lysozyme treatment, including detection at 10 1 cfu of input material (Table 1), which was not achieved before lysozyme addition (data not shown).…”

Diverse microbial interactions with the basement membrane barrier

“…Common features of CWPs are an N-terminal signal peptide followed by a so-called A region or domain, segments of repeated domains and a characteristic C-terminal sorting signal. The sorting signal contains an important cell-wall-anchoring site or LPXTG motif, which covalently binds to the cell wall [10,11]. However, it has recently been shown that the collagen-binding adhesin Slr of Gram-positive Streptococcus pyogenes lacks the LPXTG motif, but uses a cell-wall-anchoring TLIA lipobox instead [12].…”