Nonreducing SDS-PAGE analysis of the stable AT-protease complex formation with wild-type and mutant APC. An equimolar concentration (2 μM) of either wild-type (lanes 4-6) or mutant APC (lanes 7-9) was incubated with AT for 30 minutes in the absence (lanes 4 and 7) or presence of 4 μM pentasaccharide (lanes 5 and 8) or the approximately 70-saccharide heparin (lanes 6 and 9) in 20-μL reactions in TBS/Ca²⁺. Five microliters of 5 × nonreducing sample buffer was added to each reaction and the samples were boiled for 5 minutes and applied on 10% SDS gel. The stable mutant protease-AT complexes migrated as high-molecular-weight bands on lanes 8 and 9. The free forms of AT, wild-type, and mutant APC are shown in lanes 1-3, respectively. Lane 10 is molecular mass standard in kDa.