| Autor: |
Jiao Li, Long Han, Vallese, Francesca, Ziqiao Ding, Choi, Sylvia K., Sangjin Hong, Yanmei Luo, Bin Liu, Chun Kit Chan, Tajkhorshid, Emad, Jiapeng Zhu, Clarke, Oliver, Kai Zhang, Gennis, Robert |
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| Zdroj: |
Proceedings of the National Academy of Sciences of the United States of America; 8/24/2021, Vol. 118 Issue 34, p1-10, 10p |
| Abstrakt: |
Two independent structures of the proton-pumping, respiratory cytochrome bo3 ubiquinol oxidase (cyt bo3) have been determined by cryogenic electron microscopy (cryo-EM) in styrene-maleic acid (SMA) copolymer nanodiscs and in membrane scaffold protein (MSP) nanodiscs to 2.55- and 2.19-Å resolution, respectively. The structures include the metal redox centers (heme b, heme o3, and CuB), the redox-active cross-linked histidine-tyrosine cofactor, and the internal water molecules in the proton-conducting D channel. Each structure also contains one equivalent of ubiquinone-8 (UQ8) in the substrate binding site as well as several phospholipid molecules. The isoprene side chain of UQ8 is clamped within a hydrophobic groove in subunit I by transmembrane helix TM0, which is only present in quinol oxidases and not in the closely related cytochrome c oxidases. Both structures show carbonyl O1 of the UQ8 headgroup hydrogen bonded to D75I and R71I. In both structures, residue H98I occupies two conformations. In conformation 1, H98I forms a hydrogen bond with carbonyl O4 of the UQ8 headgroup, but in conformation 2, the imidazole side chain of H98I has flipped to form a hydrogen bond with E14I at the N-terminal end of TM0. We propose that H98I dynamics facilitate proton transfer from ubiquinol to the periplasmic aqueous phase during oxidation of the substrate. Computational studies show that TM0 creates a channel, allowing access of water to the ubiquinol headgroup and to H98I. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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