Yu N, Cao Y, Mager S, Lester H A
Division of Biology, California Institute of Technology, Pasadena 91125, USA.
FEBS Lett. 1998 Apr 17;426(2):174-8. doi: 10.1016/s0014-5793(98)00333-0.
Xenopus oocytes expressing the GABA transporter GAT1 were exposed to membrane-impermeant sulfhydryl reagents, resulting in decreased GABA transport current, decreased capacitive charge movements, and increased Na+ and Li+ leakage currents. Mutation of cysteine 74 to alanine (C74A) eliminated these effects. The W68S and W68L mutations significantly increased and decreased the transporter's sensitivity, respectively, to sulfhydryl reagents. At each of the positions 73 through 76, cysteine residues were accessible to external MTSET. These findings, together with recent evidence placing the HD2-HD3 loop on the extracellular side, suggest that the HD2 region does not traverse the membrane.
表达γ-氨基丁酸（GABA）转运体GAT1的非洲爪蟾卵母细胞暴露于膜不透性巯基试剂中，导致GABA转运电流降低、电容性电荷移动减少以及钠和锂泄漏电流增加。将半胱氨酸74突变为丙氨酸（C74A）消除了这些效应。W68S和W68L突变分别显著增加和降低了转运体对巯基试剂的敏感性。在73至76位的每一位点上，半胱氨酸残基均可被细胞外的甲硫基磺酸盐乙基铵（MTSET）所接触。这些发现，连同最近将HD2-HD3环置于细胞外侧的证据，表明HD2区域不穿过细胞膜。
