5.A.1.2.10
CcdA of 222 aas and 6 TMSs. The NMR structure in an oxidized and outward-facing state has been determined. CcdA consists of two inverted structural repeats of three transmembrane helices (2 x 3-TMSs). Zhou and Bushweller 2018 computationally modeled and experimentally validated an inward-facing state, which suggests that CcdA uses an elevator-type movement to shuttle the reactive cysteines across the membrane. Its structure may be relevant to other LysE superfamily transporters. Structure comparisons of CcdA, semiSWEET, Pnu, and major facilitator superfamily (MFS) transporters provide insights into membrane transporter architecture and mechanism (Zhou and Bushweller 2018).  CcdA belongs to the LysE superfamily, and thus its structure is likely to be relevant to other LysE clan transporters (Vrljic et al. 1999; Tsu and Saier 2015).