Cysteine-scanning analysis of helices TM8, TM9a, and TM9b and intervening loops in the YgfO xanthine permease: a carboxyl group is essential at ASP-276

YgfO 黄嘌呤渗透酶中螺旋 TM8、TM9a 和 TM9b 及其间环的半胱氨酸扫描分析：ASP-276 位点的羧基是必需的