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：2012
卷号：109
期号：30
页码：E2050-E2056
DOI：10.1073/pnas.1203971109
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We purified the Fo complex from the Ilyobacter tartaricus Na+-translocating F1Fo-ATP synthase and performed a biochemical and structural study. Laser-induced liquid bead ion desorption MS analysis demonstrates that all three subunits of the isolated Fo complex were present and in native stoichiometry (ab2c11). Cryoelectron microscopy of 2D crystals yielded a projection map at a resolution of 7.0 A showing electron densities from the c11 rotor ring and up to seven adjacent helices. A bundle of four helices belongs to the stator a-subunit and is in contact with c11. A fifth helix adjacent to the four-helix bundle interacts very closely with a c-subunit helix, which slightly shifts its position toward the ring center. Atomic force microscopy confirms the presence of the Fo stator, and a height profile reveals that it protrudes less from the membrane than c11. The data limit the dimensions of the subunit a/c-ring interface: Three helices from the stator region are in contact with three c11 helices. The location and distances of the stator helices impose spatial restrictions on the bacterial Fo complex.
关键词：bioenergetics ; membrane protein complex ; 2D crystallization ; ion translocation mechanism ; membrane Fo rotor-stator
