Fig. 3.

The carboxy-terminal region of CpxI is required to accelerate membrane fusion. (A) Schematic diagram of the domain organization of CpxI and of CpxI deletion mutants. The point mutations are indicated with a cross, and the amino acid changes are listed. (B) t-SNARE liposomes were incubated with v-SNARE liposomes in the absence or the presence of wild-type complexin (CpxI wt) or complexin constructs, which are either truncated at their amino-terminus (amino acids 27–134, amino acids 41–134) or their carboxy-terminus (amino acids 1–75). In addition, the double mutation R48L/R59H was introduced into CpxI 27–134 to test whether SNARE binding is required for fusion stimulation. (C) Point mutations in position 115 of CpxI reduce the stimulatory activity. Fusion was monitored and analyzed as described.