Fig. 3.

Quantitative analysis of the in vivo binding of wild-type, M46A, and N49A mutant VAMP-2 to syntaxin 1A and SNAP-25 with the yeast two-hybrid system. Two-hybrid “bait” (wild-type, M46A, and N49A mutant VAMP-2) and “prey” (syntaxin 1A and SNAP-25) plasmids were prepared as described in Materials and Methods. The reporter strain SFY526 was cotransformed with the indicated plasmid pairs, and the level of β-galactosidase activity in the transformants was determined by usingo-nitrophenyl-β-d-galactopyranoside as the substrate. The activities are expressed in Miller’s units and represent the average (±SE) taken from four independent transformants. β-Galactosidase activity was not detectable after cotransfection of the M46A mutant VAMP-2 with syntaxin 1A.