PolyP alters the thermal stability of C5b,6. C5b,6 (A-B), C5 (C), C6 (D), and C7 (E) were individually incubated with a range of concentrations of polyP_>1000, and relative fluorescence was measured as the proteins were thermally denatured. An increase in relative fluorescence indicates protein denaturation. Controls are protein without phosphate. For C5b,6 (A), arrows with numbers indicate the 3 transition phases exhibited during denaturation in the absence of polyP. (B) Focus on the second transition phase of C5b,6 (boxed region in A), where the lines from A are labeled with the different concentrations of polyP (from 0 [control] to 2 mM) that were added. PolyP induces concentration-dependent denaturation of C5b,6 and C6, but not C5 or C7. Results were similar with polyP_60-100 (not shown). Results are representative of 3 independent experiments.