start-ver=1.4
cd-journal=joma
no-vol=9
cd-vols=
no-issue=50
article-no=
start-page=50041
end-page=50048
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2024
dt-pub=20241205
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Conformational Flexibility of D1-Glu189: A Crucial Determinant in Substrate Water Selection, Positioning, and Stabilization within the Oxygen-Evolving Complex of Photosystem II
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Photosynthetic water oxidation is a vital process responsible for producing dioxygen and supplying the energy necessary to sustain life on Earth. This fundamental reaction is catalyzed by the oxygen-evolving complex (OEC) of photosystem II, which houses the Mn4CaO5 cluster as its catalytic core. In this study, we specifically focus on the D1-Glu189 amino acid residue, which serves as a direct ligand to the Mn4CaO5 cluster. Our primary goal is to explore, using density functional theory (DFT), how the conformational flexibility of the D1-Glu189 side chain influences crucial catalytic processes, particularly the selection, positioning, and stabilization of a substrate water molecule within the OEC. Our investigation is based on a hypothesis put forth by Li et al. (Nature, 2024, 626, 670), which suggests that during the transition from the S2 to S3 state, a specific water molecule temporarily coordinating with the Ca ion, referred to as O6*, may exist as a hydroxide ion (OH-). Our results demonstrate a key mechanism by which the detachment of the D1-Glu189 carboxylate group from its coordination with the Ca ion allows the creation of a specialized microenvironment within the OEC that enables the selective attraction of O6* in its deprotonated form (OH-) and stabilizes it at the catalytic metal (MnD) site. Our findings indicate that D1-Glu189 is not only a structural ligand for the Ca ion but may also play an active and dynamic role in the catalytic process, positioning O6* optimally for its subsequent participation in the oxidation sequence during the water-splitting cycle.
en-copyright=
kn-copyright=

en-aut-name=IsobeHiroshi
en-aut-sei=Isobe
en-aut-mei=Hiroshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=

en-aut-name=SuzukiTakayoshi
en-aut-sei=Suzuki
en-aut-mei=Takayoshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=

en-aut-name=SugaMichihiro
en-aut-sei=Suga
en-aut-mei=Michihiro
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=

en-aut-name=ShenJian-Ren
en-aut-sei=Shen
en-aut-mei=Jian-Ren
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=

en-aut-name=YamaguchiKizashi
en-aut-sei=Yamaguchi
en-aut-mei=Kizashi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=5
ORCID=

affil-num=1
en-affil=Research Institute for Interdisciplinary Science, Okayama University
kn-affil=

affil-num=2
en-affil=Research Institute for Interdisciplinary Science, Okayama University
kn-affil=

affil-num=3
en-affil=Research Institute for Interdisciplinary Science, Okayama University
kn-affil=

affil-num=4
en-affil=Research Institute for Interdisciplinary Science, Okayama University
kn-affil=

affil-num=5
en-affil=Center for Quantum Information and Quantum Biology, Osaka University
kn-affil=
END