Abstract
The Mn complex of photosystem II and O2-evolution activity are reconstituted in Mn-depleted photosystem II membranes in a light-dependent process called photoactivation. Recovery of O2-evolution activity requires both Mn2+ and Ca2+ in the photoactivation medium. The Mn2+ and Ca2+ dependences of both the effective rate constant and yield of photoactivation have been determined. A comparison of these data with the predictions of mathematical models for photoactivation leads to the conclusion that photoactivation occurs in two stages. The first stage, photoligation of Mn, requires light and depends primarily on Mn2+. The second stage, binding of Ca2+, is required for expression of O2-evolution activity. This two-stage model affords an excellent fit to the data and provides dissociation constants and binding stoichiometries for Ca2+ and Mn2+. We conclude that one Mn2+ ion is bound and photooxidized in the rate-determining step(s) of photoactivation. On the basis of these results and data already in the literature, the molecular details of the elementary steps in photoactivation are discussed and a mechanism of photoactivation is proposed.
| Original language | English |
|---|---|
| Pages (from-to) | 8181-8190 |
| Number of pages | 10 |
| Journal | Biochemistry |
| Volume | 28 |
| Issue number | 20 |
| Publication status | Published - 1989 |
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ASJC Scopus subject areas
- Biochemistry
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Manganese and calcium requirements for reconstitution of oxygen-evolution activity in manganese-depleted photosystem II membranes. / Miller, Anne Frances; Brudvig, Gary W.
In: Biochemistry, Vol. 28, No. 20, 1989, p. 8181-8190.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Manganese and calcium requirements for reconstitution of oxygen-evolution activity in manganese-depleted photosystem II membranes
AU - Miller, Anne Frances
AU - Brudvig, Gary W
PY - 1989
Y1 - 1989
N2 - The Mn complex of photosystem II and O2-evolution activity are reconstituted in Mn-depleted photosystem II membranes in a light-dependent process called photoactivation. Recovery of O2-evolution activity requires both Mn2+ and Ca2+ in the photoactivation medium. The Mn2+ and Ca2+ dependences of both the effective rate constant and yield of photoactivation have been determined. A comparison of these data with the predictions of mathematical models for photoactivation leads to the conclusion that photoactivation occurs in two stages. The first stage, photoligation of Mn, requires light and depends primarily on Mn2+. The second stage, binding of Ca2+, is required for expression of O2-evolution activity. This two-stage model affords an excellent fit to the data and provides dissociation constants and binding stoichiometries for Ca2+ and Mn2+. We conclude that one Mn2+ ion is bound and photooxidized in the rate-determining step(s) of photoactivation. On the basis of these results and data already in the literature, the molecular details of the elementary steps in photoactivation are discussed and a mechanism of photoactivation is proposed.
AB - The Mn complex of photosystem II and O2-evolution activity are reconstituted in Mn-depleted photosystem II membranes in a light-dependent process called photoactivation. Recovery of O2-evolution activity requires both Mn2+ and Ca2+ in the photoactivation medium. The Mn2+ and Ca2+ dependences of both the effective rate constant and yield of photoactivation have been determined. A comparison of these data with the predictions of mathematical models for photoactivation leads to the conclusion that photoactivation occurs in two stages. The first stage, photoligation of Mn, requires light and depends primarily on Mn2+. The second stage, binding of Ca2+, is required for expression of O2-evolution activity. This two-stage model affords an excellent fit to the data and provides dissociation constants and binding stoichiometries for Ca2+ and Mn2+. We conclude that one Mn2+ ion is bound and photooxidized in the rate-determining step(s) of photoactivation. On the basis of these results and data already in the literature, the molecular details of the elementary steps in photoactivation are discussed and a mechanism of photoactivation is proposed.
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M3 - Article
C2 - 2557898
AN - SCOPUS:0024960671
VL - 28
SP - 8181
EP - 8190
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 20
ER -