Analysis of Staphylococcus aureus interaction with fibrinogen /
The clumping factor (ClfA) is a cell surface associated protein of Staphylococcus aureus (S. aureus) that promotes binding of bacteria to fibrinogen/fibrin coated surfaces. ClfA consists of two major domains: a fibrinogen binding domain A (520 amino acid) followed by Asp-Ser di-peptide repeat-rich d...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=730294001&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The clumping factor (ClfA) is a cell surface associated protein of Staphylococcus aureus (S. aureus) that promotes binding of bacteria to fibrinogen/fibrin coated surfaces. ClfA consists of two major domains: a fibrinogen binding domain A (520 amino acid) followed by Asp-Ser di-peptide repeat-rich domain R (a 308 amino acid). The critical fibrinogen-binding region of ClfA has been mapped to amino acids 221-550 within domain A. The binding site in fibrinogen for ClfA resides in the C-terminus of the fibrinogen γ chain. Adherence of S. aureus cells to fibrinogen coated welts involves an interaction of ClfA protein with intact fibrinogen γ chain C-terminus. A 17 amino acid C-terminal fibrinogen γ chain peptide inhibits interaction of fibrinogen with S. aureus and the recombinant ClfA protein. The C-terminus γ chain of fibrinogen also contains a binding site for platelet integrin []. Recombinant ClfA protein is an effective inhibitor of ADP-induced platelet aggregation indicating that the binding sites of the platelet integral and the staphylococcal adhesion overlap. There are some similarities in the mechanism of interaction between integral []-fibrinogen and ClfA-fibrinogen. The [] subunit of the platelet integral contains a Ca⁺² binding EF-motif that is known to play a role in []-fibrinogen interaction. ClfA contains a potential Ca⁺² binding EF-motif at amino acids 310-321 within domain A. Deletion and site-directed mutagenesis of this EF hand in recombinant ClfA domain A resulted in a significant reduction of binding affinity for native fibrinogen and the C-terminus fibrinogen γ chain peptide. Furthermore, millimolar concentrations of Ca⁺² inhibits the binding of recombinant domain A to fibrinogen. Far UV analysis indicates that Ca⁺² ions induce a structural change within domain A of ClfA. Together, these studies indicate that Ca⁺² plays a regulatory role in the interaction of fibrinogen and domain A of ClfA. Gel permeation analysis and sedimentation ultracentrifugation analysis demonstrate that domains A and R are non globular in shape as isolated proteins and when covalently linked together (A- R) as in ClfA. Structural interactions between domains A and R seem to depend on the ionic strength of the environment. Domain R does not contain any type of ordered secondary structure and may serve as a flexible 'stalk' for R-domain containing staphylococcus surface proteins, making domain A more accessible for fibrinogen-binding. |
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| Item Description: | Vita. "Major Subject: Biochemistry". |
| Physical Description: | xi, 155 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 135-152). |