Fig. 3.

Gating residues are exposed to the cytoplasmic side. (A) Location of the 10 native Cys residues. Five cysteines are irreplaceable (blue circles). C431 (pink circle) is the primary target for inhibition by sulfhydryl reagents. (B and C) Cells were assayed for [³H]TBZ binding ability following incubation with different sulfhydryl reagents: MTSEA (B) and MTSES (C) effect on wild-type rVMAT2 (solid blue square), partial Cys-less (∆5) (solid green circle), and Δ5-Y423C (solid orange triangle). (D) [³H]TBZ binding to Δ5-M222C is inhibited by MTSES (solid green circle) and MTSET (solid orange trianlge), but not by MTSEA (solid blue square). Incubation with MTSEA before the addition of MTSES (purple diamond) and MTSET (gray star) protects against inhibition. Results presented are averages of at least two repeats, each point in duplicate; error bars indicate SE.