Fig. 1.

The membrane anchor of Ypt7 regulates its response to bound guanine nucleotide. Fusion reactions contained proteoliposomes bearing R- or QaQb-SNAREs at 1:16,000 SNARE to lipid molar ratio with 1:8,000 protein to lipid molar ratio of either Ypt7-pr (A–D) or Ypt7-tm (E–H). R- and QaQb-proteoliposomes were separately charged with No GXP, GDP, GTP, or GTPγS as indicated, and preincubated with buffer alone (black line) or 4 μM Gyp1-46 (red line) for 10 min at 27 °C. R- and QaQb-proteoliposomes were then moved to same well and mixed with 50 nM HOPS and 100 nM Qc. Content mixing of proteoliposomes was assayed by measuring the FRET between luminal Cy5 and phycoerythrin for 30 min at 27 °C. Kinetic curves of content mixing assays in this figure are representative of n ≥ 3 experiments; see SI Appendix, Fig. S1.