期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 276, 期 30, 页码 27799-27805出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M103873200
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资金
- NIAID NIH HHS [AI20624] Funding Source: Medline
Staphylococcus epidermidis is an important opportunistic pathogen and is a major cause of foreign body infections. We have characterized the ligand binding activity of SdrG, a fibrinogen-binding microbial surface component recognizing adhesive matrix molecules from S. epidermidis. Western ligand blot analysis showed that a recombinant form of the N-terminal A region of SdrG bound to the native B beta chain of fibrinogen (Fg) and to a recombinant form of the B beta chain expressed in Escherichia coli. By analyzing recombinant truncates and synthetic peptide mimetics of the Fg B beta chain, the binding site for SdrG was localized to residues 6-20 of this polypeptide. Recombinant SdrG bound to a synthetic 25-amino acid peptide (beta1-25) representing the N terminus of the Fg B beta chain with a K-D of 1.4 x 10(-7) M as determined by fluorescence polarization experiments. This was similar to the apparent K-D (0.9 x 10(-7) M) calculated from an enzyme-linked immunosorbent assay where SdrG bound immobilized Fg in a concentration-dependent manner. SdrG could recognize fibrinopeptide B (residues 1-14), but with a substantially lower affinity than that observed for SdrG binding to synthetic peptides beta1-25 and beta6-20. However, SdrG does not bind to thrombin-digested Fg. Thus, SdrG appears to target the thrombin cleavage site in the Fg B beta chain. In fact, SdrG was found to inhibit thrombin-induced fibrinogen clotting by interfering with fibrinopeptide B release.
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