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Fibronectin binding to protein A-containing staphylococci
Abstract:
Fibronectin (Fn) was found to bind to protein A-containing isolates of Staphylococcus aureus, but not to mutant strains devoid of this protein nor to clinical isolates of S. epidermidis. Fn was purified from human plasma by affinity chromatography on gelatin-Sepharose. After elution with 4 M urea, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified material detected no immunoglobulin contamination. This purified Fn was radiolabeled with 125I and used in binding assays. Quantitatively, Fn binding was directly correlated with the cellular protein A content of the various strains tested. Mannitol salt broth preculture or organisms resulted in a reduction of their cellular protein A and a decrease in Fn binding by these cells. However, soluble protein A maximally inhibited the binding of radiolabeled Fn to protein A-positive strains of staphylococci by only 50%, indicating the possibility of multiple Fn binding sites. Fn's binding to protein A-containing S. aureus strains may play a role in the pathogenicity of these organisms by promoting their attachment to and subsequent invasion of host tissues.
Insights
Fibronectin binds to Staphylococcus aureus via protein A, a key factor in bacterial infection. This interaction may promote bacterial attachment and invasion into host tissues.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Staphylococcus aureus is a significant human pathogen.
- Protein A is a surface protein found on S. aureus.
- Fibronectin is a crucial component of the extracellular matrix involved in cell adhesion and tissue repair.
Purpose of the Study:
- To investigate the binding interaction between fibronectin and Staphylococcus aureus.
- To determine the role of protein A in fibronectin binding to S. aureus.
- To explore the potential implications of this interaction in S. aureus pathogenicity.
Main Methods:
- Purification of fibronectin from human plasma using affinity chromatography.
- Radiolabeling of purified fibronectin with 125I.
- Binding assays using various S. aureus strains, including protein A-positive and mutant strains, and S. epidermidis.
- Assessment of fibronectin binding correlation with cellular protein A content.
- Evaluation of the effect of pre-culture conditions on protein A expression and fibronectin binding.
- Inhibition assays using soluble protein A.
Main Results:
- Fibronectin specifically binds to protein A-containing isolates of Staphylococcus aureus.
- Fibronectin binding is directly correlated with the cellular protein A content.
- Pre-culture in mannitol salt broth reduces cellular protein A and decreases fibronectin binding.
- Soluble protein A inhibits fibronectin binding by a maximum of 50%, suggesting additional binding sites.
Conclusions:
- Protein A on Staphylococcus aureus mediates fibronectin binding.
- Fibronectin-protein A interaction may contribute to S. aureus adherence and invasion of host tissues.
- The binding mechanism may involve multiple fibronectin-binding sites on S. aureus.