Proteolysis of lipid-free and lipid-bound apoLp-III (DMPC nanodisks). Top panel: trypsin incubations of apoLp-III. Lane 1: apoLp-III + trypsin (1:1000 mass ratio); lane 2 apoLp-III. Lanes 3 to 8 contain lipid-bound apoLp-III incubated with trypsin with apoLp-III:trypsin mass ratios of 1:100 (lane 3), 1:200 (lane 4), 1:400 (lane 5), 1:500 (lane 6), 1:1000 (lane 7), or no trypsin (lane 8). Bottom panel shows apoLp-III incubated with endoGlu-C. Lane 1 and 2: apoLp-III in the presence (lane 1) or absence (lane 2) of endoGlu-C (1:100), lane 3–5: lipid-bound apoLp-III with endoGlu-C 1:75 (lane 3), 1:100 (lane 4), and no protease (lane 5).