Phosphoglycerate kinase (PGK), present on the surface of group B streptococcus (GBS), has previously been demonstrated to bind the host proteins actin and plasminogen. The actin and plasminogen binding sites of GBS-PGK were identified using truncated GBS-PGK molecules, followed by peptide mapping. These experiments identified two actin and plasminogen binding sites located between amino acids 126-134 and 204-208 of the 398-amino acid-long GBS-PGK molecule. Substitution of the lysine residues within these regions with alanine resulted in significantly reduced binding to both actin and plasminogen. In addition, conversion of the glutamic acid residue at amino acid 133 to proline, the amino acid found at this position for the PGK protein of Streptococcus pneumoniae, also resulted in significantly reduced binding to actin and plasminogen. These results demonstrate that the lysine residues at amino acid positions 126, 127, 130, 204, and 208 along with the glutamic acid residue at amino acid position 133 are necessary for actin and plasminogen binding by GBS-PGK.
"The complex globular structure of the octameric molecule hides C-terminal lysine residues in interdimer grooves, thereby maintaining structural integrity. Similarly, an internal binding site was recently discovered for the dimeric PGK of S. agalactiae and of S. pneumoniae, and also for the M-protein PAM of S. pyogenes (Boone and Tyrrell, 2012; Fulde et al., 2013b). The interaction of the M-like protein PAM with plasminogen is mediated by two N-terminally located repeat sequences designated a1 and a2. "
[Show abstract][Hide abstract] ABSTRACT: The ability to take advantage of plasminogen and its activated form plasmin is a common mechanism used by commensal as well as pathogenic bacteria in interaction with their respective host. Hence, a huge variety of plasminogen binding proteins and activation mechanisms exist. This review solely focuses on the genus Streptococcus and, in particular, on the so-called non-activating plasminogen binding proteins. Based on structural and functional differences, as well as on their mode of surface linkaging, three groups can be assigned: M-(like) proteins, surface displayed cytoplasmatic proteins with enzymatic activities ("moonlighting proteins") and other surface proteins. Here, the plasminogen binding sites and the interaction mechanisms are compared. Recent findings on the functional consequences of these interactions on tissue degradation and immune evasion are summarized.
Frontiers in Cellular and Infection Microbiology 11/2013; 3:85. DOI:10.3389/fcimb.2013.00085 · 3.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Streptococcus pneumoniae is not only a commensal of the nasopharyngeal epithelium, but may also cause life-threatening diseases. Immune-electron microscopy studies revealed that the bacterial glycolytic enzyme, phosphoglycerate kinase (PGK), is localised on the pneumococcal surface of both encapsulated and non-capsulated strains and colocalises with plasminogen. Since pneumococci may concentrate host plasminogen (PLG) together with its activators on the bacterial cell surface to facilitate the formation of plasmin, the involvement of PGK in this process was studied. Specific binding of human or murine PLG to strain-independent PGK was documented, and surface plasmon resonance analyses indicated a high affinity interaction with the kringle domains 1-4 of PLG. Crystal structure determination of pneumococcal PGK together with peptide array analysis revealed localisation of PLG-binding site in the N-terminal region and provided structural motifs for the interaction with PLG. Based on structural analysis data, a potential interaction of PGK with tissue plasminogen activator (tPA) was proposed and experimentally confirmed by binding studies, plasmin activity assays and thrombus degradation analyses.
Thrombosis and Haemostasis 11/2013; 111(3). DOI:10.1160/TH13-05-0421 · 4.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study focuses on the impact of actin on adhesion and translocation of Enterococcus (E.) faecalis OG1RF, E. faecalis Symbioflor(®), and E. faecalis V583. Insight into the role of actin aggregation in the mediation of bacterial adhesion and translocation was provided by a two-chamber translocation assay, which employed Ptk6 cells. Determination of translocation rates, cytochalasin D treatment, and laser scanning confocal microscopic observation revealed actin as a predominant brace for enterococci to pass through the epithelial cell layer. As the three enterococci had moderate adhesion ability to actin, actin-binding proteins were isolated and characterized by LC-MS/MS. The isolated proteins were identified as pyruvate formate lyase, enolase, glyceraldehyde-3-phosphate dehydrogenase, and GroEL. All these proteins belong to two major groups of moonlighting proteins, i.e., proteins, which display additional functions other than their described major biochemical catalysis. Both groups of moonlight proteins were determined to be associated with epithelial cell binding.
Archives of Microbiology 12/2013; 196(2). DOI:10.1007/s00203-013-0943-1 · 1.67 Impact Factor
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