title: Photosynthetic water oxidation vs. mitochondrial oxygen reduction: distinct mechanistic parallels.
abstract: The photosynthetic oxygen evolving complex (PSII-OEC) and the mitochondrial cytochrome c oxidase (CcO) not only catalyze anti-parallel reactions (the OEC oxidizes water to dioxygen, whereas CcO reduces dioxygen to water), they also share a number of uncanny molecular and mechanistic similarities. Both feature a redox-active polymetallic cluster that includes a key tyrosine, and both utilize a two-phase mechanism. In one phase the polymetallic cluster undergoes four sequential one-electron transfers: In the PSII-OEC, four successive photooxidations of the photosystem II reaction center P680 (to P680(+)) allows acceptance of 4 × 1e- from the Mn(4)Ca cluster; in CcO, four reduced cytochrome c Fe(2+) cations donate 4 × 1e- to the bimetallic center. In the second phase for each enzyme, the polymetallic cluster undergoes a single four-electron transfer with the O(2)/2 H(2)O redox couple. Intriguing mechanistic similarities between these two complex redox enzymes first delineated over a decade ago by Hoganson/Proshlyakov/Babcock et al. are updated and expanded in this article.
authors.affiliation: Chemistry Department, Willamette University, Salem, OR 97301, USA. tsilvers@willamette.edu
authors.forename: Todd P
authors.initials: TP
authors.lastname: Silverstein
mesh_terms: D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D010084:Oxidation-Reduction; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D014867:Water / Q000737:chemistry / Q000378:metabolism*
chemical_list: D045332:Photosystem II Protein Complex; D014867:Water; D003576:Electron Transport Complex IV