Figure 3.

Peptide-stimulated ATPase activity of reconstituted TAP. (A) For determination of the ATPase activity of TAP, the release of inorganic γ-³²P_i from [γ-³²P]ATP was measured for 4 min at 32°C in the presence or absence of ortho-vanadate (1 mM) and/or peptides (0.8 μM) (R9LQK = RRYQKSTEL; E9D = EPGNTWDED). To demonstrate TAP-specific ATPase activity, proteoliposomes were incubated with TAP-inhibitor ICP47 (5 μM) for 40 min on ice before addition of peptides. (B) Specificity pattern of the vanadate-sensitive ATPase activity analyzed by combinatorial peptide libraries. Combinatorial peptide libraries X₈O (2.4 μM) were incubated with TAP-containing proteoliposomes.