The binding of native DNA to the collagen-like segment of Clq

Our study was undertaken to determine if native DNA (dsDNA), which is known to bind to collagen, also binds to the collagen-like segment of Clq (CLS). Three methods were employed to demonstrate the binding of dsDNA to CLS: (1) Six human sera and a mouse monoclonal antibody to dsDNA were employed in an enzyme linked immunosorbent assay to detect CLS bound dsDNA. When applied to CLS bound dsDNA, sera with antibodies to dsDNA and monoclonal antibody to DNA yielded mean OD values of greater than or equal to 0.6, significantly higher than those values obtained from control experiments (mean OD less than or equal to 0.2, p less than or equal to 0.003). (2) In a solid phase immunoassay radiolabelled DNA (3H DNA) was exposed to increasing amounts of solid phase adherent CLS. The binding of 3H DNA to the solid phase was substantially greater (more than a 30-fold increase) when the solid phase had been precoated with CLS. (3) dsDNA binding to CLS was demonstrated further by incubating electrophoretically resolved CLS with dsDNA and localizing the bound dsDNA by ethidium bromide staining. Our results indicate the dsDNA binds to CLS. Since CLS is the binding site for Clr and then Clr2Cls2, molecules which bind to CLS, such as dsDNA, could be important factors affecting Cl activation.