TY - JOUR
T1 - Recent pulsed EPR studies of the Photosystem II oxygen-evolving complex
T2 - Implications as to water oxidation mechanisms
AU - Britt, R. David
AU - Campbell, Kristy A.
AU - Peloquin, Jeffrey M.
AU - Gilchrist, M. Lane
AU - Aznar, Constantino P.
AU - Dicus, Michelle M.
AU - Robblee, John
AU - Messinger, Johannes
PY - 2004/4/12
Y1 - 2004/4/12
N2 - The pulsed electron paramagnetic resonance (EPR) methods of electron spin echo envelope modulation (ESEEM) and electron spin echo-electron nuclear double resonance (ESE-ENDOR) are used to investigate the structure of the Photosystem II oxygen-evolving complex (OEC), including the paramagnetic manganese cluster and its immediate surroundings. Recent unpublished results from the pulsed EPR laboratory at UC-Davis are discussed, along with aspects of recent publications, with a focus on substrate and cofactor interactions. New data on the proximity of exchangeable deuterons around the Mn cluster poised in the S 0-state are presented and interpreted. These pulsed EPR results are used in an evaluation of several recently proposed mechanisms for PSII water oxidation. We strongly favor mechanistic models where the substrate waters bind within the OEC early in the S-state cycle. Models in which the O-O bond is formed by a nucleophilic attack by a Ca2+-bound water on a strong S4-state electrophile provide a good match to the pulsed EPR data.
AB - The pulsed electron paramagnetic resonance (EPR) methods of electron spin echo envelope modulation (ESEEM) and electron spin echo-electron nuclear double resonance (ESE-ENDOR) are used to investigate the structure of the Photosystem II oxygen-evolving complex (OEC), including the paramagnetic manganese cluster and its immediate surroundings. Recent unpublished results from the pulsed EPR laboratory at UC-Davis are discussed, along with aspects of recent publications, with a focus on substrate and cofactor interactions. New data on the proximity of exchangeable deuterons around the Mn cluster poised in the S 0-state are presented and interpreted. These pulsed EPR results are used in an evaluation of several recently proposed mechanisms for PSII water oxidation. We strongly favor mechanistic models where the substrate waters bind within the OEC early in the S-state cycle. Models in which the O-O bond is formed by a nucleophilic attack by a Ca2+-bound water on a strong S4-state electrophile provide a good match to the pulsed EPR data.
KW - CHL
KW - Chlorophyll
KW - Continuous wave electron paramagnetic resonance
KW - CW EPR
KW - DCMU
KW - Dichlorophenyldimethyl urea
KW - Electron nuclear double resonance
KW - Electron spin echo
KW - ENDOR
KW - ESE
KW - ESEEM
KW - Multiline EPR signal
KW - S-state
KW - Substrate water binding
UR - http://www.scopus.com/inward/record.url?scp=1942440420&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2003.11.009
DO - 10.1016/j.bbabio.2003.11.009
M3 - Review article
C2 - 15100028
AN - SCOPUS:1942440420
SN - 0005-2728
VL - 1655
SP - 158
EP - 171
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 1-3
ER -