Figure 1. Structure and function of SemiSWEET.

(a) Time course of [¹⁴C]-sucrose uptake by proteoliposomes containing EcSemiSWEET (solid black squares) or empty control liposomes (open black squares) (mean± s.e.m., n=6). (b) Plots of the sucrose uptake rate versus the extra-liposomal sucrose concentration (mean±s.e.m., n=3). (c) Overall structure of the inward-open SemiSWEET dimer, viewed parallel to the membrane (upper) or from the intracellular side (lower). In the ribbon representations (left), TM1, TM2, and TM3 of one protomer are coloured blue, green and red, respectively, and the other protomer is coloured grey. In the surface representations (right), the dimer is coloured according to the surface electrostatic potential. The cut-away surface is shown in the parallel view. The twofold axis is indicated by dashed lines and an almond-shaped symbol. (d) Overall structure of the outward-open SemiSWEET dimer, viewed parallel to the membrane (upper) and from the extracellular side (lower), coloured as in c.