期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：21
页码：9903-9908
DOI：10.1073/pnas.1004515107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Many independent lines of evidence indicate that the lactose permease of Escherichia coli (LacY) is highly dynamic and that sugar binding causes closing of a large inward-facing cavity with opening of a wide outward-facing hydrophilic cavity. Therefore, lactose/H+ symport catalyzed by LacY very likely involves a global conformational change that allows alternating access of single sugar- and H+-binding sites to either side of the membrane (the alternating access model). The x-ray crystal structures of LacY, as well as the majority of spectroscopic studies, use purified protein in detergent micelles. By using site-directed alkylation, we now demonstrate that sugar binding induces virtually the same global conformational change in LacY whether the protein is in the native bacterial membrane or is solubilized and purified in detergent. The results also indicate that the x-ray crystal structure reflects the structure of wild-type LacY in the native membrane in the absence of sugar.
关键词：lactose ; permease ; symport ; transport ; membrane proteins
