title: Redox potential of the primary plastoquinone electron acceptor Q(A) in photosystem II from Thermosynechococcus elongatus determined by spectroelectrochemistry.
abstract: The redox potential of the primary plastoquinone electron acceptor Q(A), E(m)(Q(A)/Q(A)(-)), in an oxygen-evolving photosystem (PS) II complex from a thermophilic cyanobacterium Thermosynechococcus elongatus was determined to be -140 +/- 2 mV vs. SHE by thin-layer cell spectroelectrochemistry for the first time. The E(m)(Q(A)/Q(A)(-)) value obtained here together with the recently determined redox potential of pheophytin (Phe) a [Kato et al. (2009) Proc. Natl. Acad. Sci. U.S.A. 106, 17365-17370] yields -330 to -370 mV for the free energy change by electron transfer from Phe a(-) to Q(A) and provides a renewed picture for the energetics on the electron acceptor side in PS II.
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Tadao
authors.initials: T
authors.lastname: Shibamoto
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kato
authors.forename: Miwa
authors.initials: M
authors.lastname: Sugiura
authors.forename: Tadashi
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D004563:Electrochemistry / Q000379:methods*; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010971:Plastoquinone / Q000378:metabolism*; D013057:Spectrum Analysis / Q000379:methods*; D046940:Synechococcus / Q000378:metabolism*
chemical_list: D045332:Photosystem II Protein Complex; D010971:Plastoquinone