Figure 6.

AP-1 stimulates ArfGAP1 activity. Arf1 was activated in the presence of [γ-³²P]GTP on liposomes presenting LY (filled symbols) or LA peptides (empty symbols). After incubation with ArfGAP1 and/or effectors, free phosphate released by GTP hydrolysis was measured. The time course of GTP hydrolysis in the presence of 1 μM catalytic domain of ArfGAP1 (GAP136) alone (circles) or in the presence of 0.25 μM COPI coatomer (triangles) is shown in A, and with 0.25 μM purified AP-1 (squares) in B. No hydrolysis was induced by AP-1 without ArfGAP1 (diamonds). The concentration dependence of AP-1 stimulation of the catalytic domain and of full-length ArfGAP1 (FL-GAP; 0.5 nM) is shown in C and D, respectively.