Electrogenicity of electron and proton transfer at the oxidizing side of photosystem II

Autor(en): Haumann, M
Mulkidjanian, A 
Junge, W 
Stichwörter: Biochemistry & Molecular Biology; HISTIDINE OXIDATION; MANGANESE; OXYGEN-EVOLVING COMPLEX; PARAMAGNETIC-RESONANCE; PARTICLES; PHOTOSYNTHETIC WATER OXIDATION; REDOX-ACTIVE TYROSINE; REDUCTION KINETICS; RELEASE; THYLAKOID MEMBRANES
Erscheinungsdatum: 1997
Herausgeber: AMER CHEMICAL SOC
Journal: BIOCHEMISTRY
Volumen: 36
Ausgabe: 31
Startseite: 9304
Seitenende: 9315
Zusammenfassung: 
The electrogenicity of electron and proton transfer at the oxidizing side of PSII was monitored by transmembrane electrochromism of carotenoids in thylakoids and, independently, by electrometry in oxygen-evolving photosystem II core particles. It yielded dielectrically weighted distances between cofactors, They were related to the one between Y-Z(ox) and Q(A)(-) (=100%). The electron transfer from Y-Z to P-680(+) ranged over a relative distance of 15%, while the one from Mn-4 to Y-Z(ox) ranged over less than 3.5%. The latter result placed Mn-4 and Y-Z at about the same weighted depth in the membrane. The oxidation of cofactor X by Y-Z(ox) during S-2 --> S-3 ranged over 10%. We tentatively attributed 7% to proton transfer into the lumen and 3% to electron transfer, in line with our notion that one proton is liberated from X-ox itself. This placed X at the same depth in the membrane as Mn. Proton release upon the final oxidation of water during the oxygen-evolving step S-4 --> S-0 revealed relative electrogenic components of 5.5% in care particles and between 10.5% (pH 7.4) and 2% (pH 6.2) in thylakoids. The former likely reflected proton transfer from bound water into the lumen and the latter to intraprotein bases that were created in the foregoing transitions, A tentative scheme for the arrangement of cofactors al the oxidizing side of photosystem II is presented.
ISSN: 00062960
DOI: 10.1021/bi963114p

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