PMID:7980398
| Citation |
Van Iwaarden, JF, Pikaar, JC, Storm, J, Brouwer, E, Verhoef, J, Oosting, RS, van Golde, LM and van Strijp, JA (1994) Binding of surfactant protein A to the lipid A moiety of bacterial lipopolysaccharides. Biochem. J. 303 ( Pt 2):407-11 |
|---|---|
| Abstract |
Surfactant protein A (SP-A) enhances the phagocytosis of opsonized and non-opsonized bacteria by alveolar macrophages, but it is not known with which component of the bacterial surface it associates. We investigated the interaction of SP-A with lipopolysaccharides (LPS), which are important biologically active constituents of the outer membranes of Gram-negative bacteria. Flow cytometry was used to study the binding of fluorescein isothiocyanate-labelled SP-A either to LPS of various chain lengths coupled to magnetic beads or to Gram-negative bacteria. The binding of SP-A to LPS-coated beads was saturable, both time- and concentration-dependent, and required both Ca2+ and Na+. SP-A bound to the lipid A moiety of LPS and to LPS from either the Re-mutant of Salmonella minnesota or the J5-mutant of Escherichia coli. In contrast, it did not bind to O111 LPS of E. coli, suggesting that SP-A binds only to rough LPS. The binding of SP-A to LPS was not affected by mannan and heparin or by deglycosylation of the SP-A, indicating that the carbohydrate-binding domain and the carbohydrate moiety of SP-A are not involved in its interaction with LPS. We also observed saturable and concentration-dependent binding of SP-A to the live J5 mutant of whole E. coli, but not to its O111 mutant. In addition, Re LPS aggregated in the presence of SP-A, Ca2+ and Na+. We conclude that SP-A associates with LPS via the lipid A moiety of rough LPS and may be involved in the anti-bacterial defences of the lung. |
| Links | |
| Keywords |
Bronchoalveolar Lavage Fluid/chemistry; Calcium/pharmacology; Dose-Response Relationship, Drug; Escherichia coli/genetics; Escherichia coli/metabolism; Flow Cytometry; Fluorescein-5-isothiocyanate/chemistry; Humans; Lipid A/metabolism; Lipopolysaccharides/metabolism; Microspheres; Mutation/genetics; Protein Binding/drug effects; Proteolipids/metabolism; Pulmonary Surfactant-Associated Protein A; Pulmonary Surfactant-Associated Proteins; Pulmonary Surfactants/metabolism; Salmonella/genetics; Salmonella/metabolism; Sodium/pharmacology |
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