A nanosecond time-resolved XFEL analysis of structural changes associated with CO release from cytochrome c oxidase

作者：Shimada Atsuhiro; Kubo Minoru; Baba Seiki; Yamashita Keitaro; Hirata Kunio; Ueno Go; Nomura Takashi; Kimura Tetsunari; Shinzawa Itoh Kyoko; Baba Junpei; Hatano Keita; Eto Yuki; Miyamoto Akari; Murakami Hironori; Kumasaka Takashi; Owada Shigeki; Tono Kensuke; Yabashi Makina; Yamaguchi Yoshihiro; Yanagisawa Sachiko; Sakaguchi Miyuki; Ogura Takashi; Komiya Ryo; Yan Jiwang; Yamashita Eiki; Yamamoto Masaki; Ago Hideo^*; Yoshikawa Shinya^*; Tsukihara Tomitake^*

来源：Science Advances, 2017, 3(7): e1603042.

DOI：10.1126/sciadv.1603042

Bovine cytochrome c oxidase (CcO), a 420-kDa membrane protein, pumps protons using electrostatic repulsion between protons transferred through a water channel and net positive charges created by oxidation of heme a (Fe-a) for reduction of O-2 at heme a(3) (Fe-a3). For this process to function properly, timing is essential: The channel must be closed after collection of the protons to be pumped and before Fea oxidation. If the channel were to remain open, spontaneous backflow of the collected protons would occur. For elucidation of the channel closure mechanism, the opening of the channel, which occurs upon release of CO from CcO, is investigated by newly developed time-resolved x-ray free-electron laser and infrared techniques with nanosecond time resolution. The opening process indicates that Cu-B senses completion of proton collection and binds O-2 before binding to Fe-a3 to close the water channel using a conformational relay system, which includes Cu-B, heme a(3), and a transmembrane helix, to block backflow of the collected protons.

• 出版日期2017-7
• 单位RIKEN