Primary Citation of Related Structures: 5B1A, 5B1B, 7YPY
PubMed Abstract:
Bovine heart cytochrome c oxidase (CcO) pumps four proton equivalents per catalytic cycle through the H-pathway, a proton-conducting pathway, which includes a hydrogen bond network and a water channel operating in tandem. Protons are transferred by H 3 O + through the water channel from the N-side into the hydrogen bond network, where they are pumped to the P-side by electrostatic repulsion between protons and net positive charges created at heme a as a result of electron donation to O 2 bound to heme a 3 To block backward proton movement, the water channel remains closed after O 2 binding until the sequential four-proton pumping process is complete ...
Bovine heart cytochrome c oxidase (CcO) pumps four proton equivalents per catalytic cycle through the H-pathway, a proton-conducting pathway, which includes a hydrogen bond network and a water channel operating in tandem. Protons are transferred by H 3 O + through the water channel from the N-side into the hydrogen bond network, where they are pumped to the P-side by electrostatic repulsion between protons and net positive charges created at heme a as a result of electron donation to O 2 bound to heme a 3 To block backward proton movement, the water channel remains closed after O 2 binding until the sequential four-proton pumping process is complete. Thus, the hydrogen bond network must collect four proton equivalents before O 2 binding. However, a region with the capacity to accept four proton equivalents was not discernable in the x-ray structures of the hydrogen bond network. The present x-ray structures of oxidized/reduced bovine CcO are improved from 1.8/1.9 to 1.5/1.6 Å resolution, increasing the structural information by 1.7/1.6 times and revealing that a large water cluster, which includes a Mg 2+ ion, is linked to the H-pathway. The cluster contains enough proton acceptor groups to retain four proton equivalents. The redox-coupled x-ray structural changes in Glu 198 , which bridges the Mg 2+ and Cu A (the initial electron acceptor from cytochrome c) sites, suggest that the Cu A -Glu 198 -Mg 2+ system drives redox-coupled transfer of protons pooled in the water cluster to the H-pathway. Thus, these x-ray structures indicate that the Mg 2+ -containing water cluster is the crucial structural element providing the effective proton pumping in bovine CcO.
Organizational Affiliation:
From the Picobiology Institute and yoshi@sci.u-hyogo.ac.jp.
RA [auth C] UB [auth P] VA [auth G] XA [auth G] YB [auth T]
RA [auth C], UB [auth P], VA [auth G], XA [auth G], YB [auth T], ZB [auth T]
(1S)-2-{[(2-AMINOETHOXY)(HYDROXY)PHOSPHORYL]OXY}-1-[(STEAROYLOXY)METHYL]ETHYL (5E,8E,11E,14E)-ICOSA-5,8,11,14-TETRAENOATE C43 H78 N O8 P ANRKEHNWXKCXDB-BHFWLYLHSA-N
(7R,17E,20E)-4-HYDROXY-N,N,N-TRIMETHYL-9-OXO-7-[(PALMITOYLOXY)METHYL]-3,5,8-TRIOXA-4-PHOSPHAHEXACOSA-17,20-DIEN-1-AMINIUM 4-OXIDE C42 H81 N O8 P JLPULHDHAOZNQI-AUSZDXHESA-O
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