title: The location of binding sites on C1q for DNA.
abstract: Previous studies have suggested that C1q reacts with DNA via both the globular region of C1q (GR) and the collagen-like region of C1q (CLR). In this study, the binding of dsDNA and ssDNA to GR and CLR was quantitated by a solid-phase assay. Both dsDNA and ssDNA bound to the GR and CLR of C1q in an ionic strength-dependent manner. Under physiologic salt concentrations, however, dsDNA and ssDNA bound preferentially to CLR and not to GR. The binding of dsDNA to C1q was not affected by heat inactivation of C1q or its exposure to pH 4.45, which abolished the binding of heat-aggregated human IgG (AHG) with C1q. The preincubation of the solid-phase C1q with AHG did not decrease the binding of dsDNA or ssDNA to the solid-phase C1q. These results indicate that the major sites for binding DNA to C1q are located in the CLR of C1q and are not overlapping with those for AHG or immune complexes.
authors.affiliation: Department of Medicine, University of Washington, Seattle 98195.
authors.forename: S
authors.initials: S
authors.lastname: Uwatoko
authors.forename: M
authors.initials: M
authors.lastname: Mannik
mesh_terms: D001665:Binding Sites; D003094:Collagen; D015922:Complement C1q / Q000378:metabolism* / Q000648:ultrastructure; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000648:ultrastructure; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007136:Immunoglobulins / Q000378:metabolism; D066298:In Vitro Techniques; D010446:Peptide Fragments / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D007136:Immunoglobulins; D010446:Peptide Fragments; D015922:Complement C1q; D003094:Collagen; D004247:DNA