4.A.7.1.1
The L-ascorbate transporting and phosphorylating group translocator, SgaTBA or UlaCBA (SgaT = UlaA = YjfS; SgaB = UlaB = YjfT; SgaA = UlaC = PtxA = YjfU) (Hvorup et al., 2003; Zhang et al., 2003). Two conformations of the 3-d structure have been determined at 1.65 and 2.35 Å resolution, respectively (Luo et al., 2015). UlaA (SgaT) forms a homodimer with a novel fold. Each UlaA protomer consists of 11 TMSs arranged into a 'V-motif' domain and a 'core' domain. The V motifs form the interface between the two protomers, and the core-domain residues coordinate vitamin C. Alternating access of the substrate to the two sides of the cell membrane may be achieved through rigid-body rotation of the core relative to the V motif (Luo et al., 2015; Zhang et al., 2003). This structure does not resemble the ChbC structure (TC# 4.A.3.2.8).