Journal: The Journal of Immunology Author Choice
Article Title: A Conformational Change of Complement C5 Is Required for Thrombin-Mediated Cleavage, Revealed by a Novel Ex Vivo Human Whole Blood Model Preserving Full Thrombin Activity
doi: 10.4049/jimmunol.2001471
Figure Lengend Snippet: Cleavage of purified C5 by thrombin, as detected by protein staining and Western blot. (A) SDS-PAGE on purified C5 (500 nM) from Comptech, Quidel, and our MgCl2 affinity-purified C5 eluted under mild conditions using a 2 M MgCl2 solution, incubated with thrombin (100 nM) for 0, 15, and 60 min at 37°C before the addition of lepirudin (1 μM). At 0 min, lepirudin was added before thrombin. Intact and cleaved α-chain is indicated by α and α′ respectively, β-chain is indicated with β. The gel was stained with Coomassie brilliant blue. (B) Purified C5 (500 nM) from Comptech was incubated with thrombin (100 nM) for different time intervals (7.5 min to 20 h), as indicated on top of a representative SDS-PAGE stained with Coomassie brilliant blue. Reference proteins are shown in separate lanes; thrombin (Thr), lepirudin (Lep), and C5 (C5), and an m.w. reference (M). C5 α-chain (α) and β-chain (β) are indicated in the label on the right-hand side of the figure, so are the primary (α′) and secondary (α′′ cleavage fragments, together with thrombin and C5a. (C) Purified Comptech C5 (500 nM) was incubated for 1 h at 37°C with PBS, thrombin (100 nM), thrombin (100 nM) in the presence of lepirudin (1 μM), or cobra venom factor (CVF). C5a-containing fragments were detected by Western blot using a polyclonal antibody against C5a. (D) GPRP-plasma was incubated with thrombin (400 nM) alone or in the presence of lepirudin (7 μM), purified Comptech C5 (60 μg/ml) alone or in the presence of thrombin, or the combination of purified C5 (60 μg/ml), thrombin (400 nM), and lepirudin (7 μM), for 16 h at 37°C. C5a-containing fragments were immunoprecipitated using a monoclonal antibody against C5a (clone 137-26) and detected by Western blot as described for (B). (E) Identical conditions as described for (C), but incubations were performed in serum from a C5-deficient individual instead of in GPRP-plasma. All samples were run under reducing conditions (A–E). M, m.w. markers with size indicated in kDa.
Article Snippet: Proteins were transferred onto an immunoblot polyvinylidene fluoride membrane (Bio-Rad) and blotted using rabbit polyclonal IgG anti-prothrombin (Molecular innovations; Novi, MI) followed by an HRP-linked goat anti-rabbit-IgG (Southern Biotech, Birmingham, AL).
Techniques: Purification, Staining, Western Blot, SDS Page, Affinity Purification, Incubation, Combined Bisulfite Restriction Analysis Assay, Immunoprecipitation