2015
DOI: 10.1021/acs.jpcb.5b03559
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Removal of Ca2+ from the Oxygen-Evolving Complex in Photosystem II Has Minimal Effect on the Mn4O5 Core Structure: A Polarized Mn X-ray Absorption Spectroscopy Study

Abstract: Ca2+-depleted and Ca2+-reconstituted spinach photosystem II was studied using polarized X-ray absorption spectroscopy of oriented PS II preparations to investigate the structural and functional role of the Ca2+ ion in the Mn4O5Ca cluster of the oxygen-evolving complex (OEC). Samples were prepared by low pH/citrate treatment as one-dimensionally ordered membrane layers and poised in the Ca2+-depleted S1 (S1′) and S2 (S2′) states, the S2′YZ• state, at which point the catalytic cycle of water oxidation is inhibit… Show more

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Cited by 22 publications
(20 citation statements)
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“…However, the potential-energy curve of the O H 3 O + ···O W3 H-bond is asymmetric, which suggests that it is not a low-barrier H-bond and the H atom is predominantly populated at the O H 3 O + moiety (Figure b and Figure S4). On the basis of these findings, it seems most likely that H 3 O + , and not [H 2 O···H···OH 2 ] + , can exist at the Ca 2+ -depleted Mn 4 O 5 cluster in particular at low pH, which is in line with those proposed by Lohmiller et al on the basis of polarized Mn X-ray absorption spectroscopy …”
Section: Results and Discussionsupporting
confidence: 63%
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“…However, the potential-energy curve of the O H 3 O + ···O W3 H-bond is asymmetric, which suggests that it is not a low-barrier H-bond and the H atom is predominantly populated at the O H 3 O + moiety (Figure b and Figure S4). On the basis of these findings, it seems most likely that H 3 O + , and not [H 2 O···H···OH 2 ] + , can exist at the Ca 2+ -depleted Mn 4 O 5 cluster in particular at low pH, which is in line with those proposed by Lohmiller et al on the basis of polarized Mn X-ray absorption spectroscopy …”
Section: Results and Discussionsupporting
confidence: 63%
“…can exist at the Ca 2+ -depleted Mn 4 O 5 cluster in particular at low pH, which is in line with those proposed by Lohmiller et al on the basis of polarized Mn X-ray absorption spectroscopy. 21 As previously reported, 46 when the Ca 2+ binding site is occupied by H 2 O, instead of H 3 O + , W3 reorients and alters the H-bond partner from W7 to O5 to compensate for the loss of the Ca 2+ charge. The loss of the W3•••W7 H-bond disrupts the formation of the diamond-shaped cluster of water molecules [i.e., W3 and W5−W7 5 (Figure 3a,b)] near TyrZ.…”
Section: ■ Methodsmentioning
confidence: 99%
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“…Some fraction of centers lacking Ca may be present naturally in vivo prior to protein isolation, or Ca depletion could have been induced due to the sample preparation procedure. Indeed, Ca is known to be easily lost from the OEC while otherwise maintaining the general structure of the active site ( 68 ).…”
Section: Discussionmentioning
confidence: 99%
“…Therefore, Ca-deficient plants also showed type II behavior for the same reason as the Mn deficiency. However, the contribution of Ca to the function of OEC is relatively minor when compared to Mn [83], which gave higher Y(II) and Y(I) values in Ca-deficient plants than those in Mn deficiency-treated plants (Figure 3).…”
Section: Discussionmentioning
confidence: 99%