APC cleavage of the heavy chain of factor Va. (Top Panel) Purified factor V was treated with glycosidases, activated with thrombin, and incubated with APC for 0, 5, 10, 15, and 20 minutes without the addition of phospholipids under the conditions described in the Materials and Methods. Disappearance of the factor Va heavy chain indicates cleavage by APC. The samples were run on SDS-PAGE and blotted with specific anti-heavy chain antibodies. (Bottom Panel) Reaction conditions were the same for the samples seen in the top panel, except for the presence of phospholipid vesicles (phosphatidyl serine:phosphatidyl choline = 1:9). In both panels, the position of migration of the heavy chains (HC) is indicated by the arrows. Note that the deglycosylated heavy chain migrated further than the untreated control heavy chain.