Abstract
Perturbation of the catalytic inorganic core (Mn4Ca 1OxCly) of the photosystem II-water-oxidizing complex (PSII-WOC) isolated from spinach is examined by substitution of Ca 2+ with cadmium(II) during core assembly. Cd2+ inhibits the yield of reconstitution of O2-evolution activity, called photoactivation, starting from the free inorganic cofactors and the cofactor-depleted apo-WOC-PSII complex. Ca2+ affinity increases following photooxidation of the first Mn2+ to Mn3+ bound to the 'high-affinity' site. Ca2+ binding occurs in the dark and is the slowest overall step of photoactivation (IM1→IM 1* step). Cd2+ competitively blocks the binding of Ca2+ to its functional site with 10- to 30-fold higher affinity, but does not influence the binding of Mn2+ to its high-affinity site. By contrast, even 10-fold higher concentrations of Cd2+ have no effect on O2-evolution activity in intact PSII-WOC. Paradoxically, Cd 2+ both inhibits photoactivation yield, while accelerating the rate of photoassembly of active centres 10-fold relative to Ca2+. Cd 2+ increases the kinetic stability of the photooxidized Mn 3+ assembly intermediate(s) by twofold (mean lifetime for dark decay). The rate data provide evidence that Cd2+ binding following photooxidation of the first Mn3+, IM1→IM 1*, causes three outcomes: (i) a longer intermediate lifetime that slows IM1 decay to IM0 by charge recombination, (ii) 10-fold higher probability of attaining the degrees of freedom (either or both cofactor and protein d.f.) needed to bind and photooxidize the remaining 3 Mn2+ that form the functional cluster, and (iii) increased lability of Cd2+ following Mn4 cluster assembly results in (re)exchange of Cd2+ by Ca2+ which restores active O2-evolving centres. Prior EPR spectroscopic data provide evidence for an oxo-bridged assembly intermediate, Mn 3+(μ-O2-)Ca2+, for IM1*. We postulate an analogous inhibited intermediate with Cd2+ replacing Ca2+.
| Original language | English |
|---|---|
| Pages (from-to) | 1253-1261 |
| Number of pages | 9 |
| Journal | Philosophical Transactions of the Royal Society B: Biological Sciences |
| Volume | 363 |
| Issue number | 1494 |
| DOIs | |
| Publication status | Published - Mar 27 2008 |
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Keywords
- Calcium
- Manganese
- Oxygen evolution
- Photosynthesis
- Photosystem II
- Water oxidation
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)
- Agricultural and Biological Sciences (miscellaneous)
Cite this
Calcium controls the assembly of the photosynthetic water-oxidizing complex : A cadmium(II) inorganic mutant of the Mn4Ca core. / Bartlett, John E.; Baranov, Sergei V.; Ananyev, Gennady M.; Dismukes, G Charles.
In: Philosophical Transactions of the Royal Society B: Biological Sciences, Vol. 363, No. 1494, 27.03.2008, p. 1253-1261.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Calcium controls the assembly of the photosynthetic water-oxidizing complex
T2 - A cadmium(II) inorganic mutant of the Mn4Ca core
AU - Bartlett, John E.
AU - Baranov, Sergei V.
AU - Ananyev, Gennady M.
AU - Dismukes, G Charles
PY - 2008/3/27
Y1 - 2008/3/27
N2 - Perturbation of the catalytic inorganic core (Mn4Ca 1OxCly) of the photosystem II-water-oxidizing complex (PSII-WOC) isolated from spinach is examined by substitution of Ca 2+ with cadmium(II) during core assembly. Cd2+ inhibits the yield of reconstitution of O2-evolution activity, called photoactivation, starting from the free inorganic cofactors and the cofactor-depleted apo-WOC-PSII complex. Ca2+ affinity increases following photooxidation of the first Mn2+ to Mn3+ bound to the 'high-affinity' site. Ca2+ binding occurs in the dark and is the slowest overall step of photoactivation (IM1→IM 1* step). Cd2+ competitively blocks the binding of Ca2+ to its functional site with 10- to 30-fold higher affinity, but does not influence the binding of Mn2+ to its high-affinity site. By contrast, even 10-fold higher concentrations of Cd2+ have no effect on O2-evolution activity in intact PSII-WOC. Paradoxically, Cd 2+ both inhibits photoactivation yield, while accelerating the rate of photoassembly of active centres 10-fold relative to Ca2+. Cd 2+ increases the kinetic stability of the photooxidized Mn 3+ assembly intermediate(s) by twofold (mean lifetime for dark decay). The rate data provide evidence that Cd2+ binding following photooxidation of the first Mn3+, IM1→IM 1*, causes three outcomes: (i) a longer intermediate lifetime that slows IM1 decay to IM0 by charge recombination, (ii) 10-fold higher probability of attaining the degrees of freedom (either or both cofactor and protein d.f.) needed to bind and photooxidize the remaining 3 Mn2+ that form the functional cluster, and (iii) increased lability of Cd2+ following Mn4 cluster assembly results in (re)exchange of Cd2+ by Ca2+ which restores active O2-evolving centres. Prior EPR spectroscopic data provide evidence for an oxo-bridged assembly intermediate, Mn 3+(μ-O2-)Ca2+, for IM1*. We postulate an analogous inhibited intermediate with Cd2+ replacing Ca2+.
AB - Perturbation of the catalytic inorganic core (Mn4Ca 1OxCly) of the photosystem II-water-oxidizing complex (PSII-WOC) isolated from spinach is examined by substitution of Ca 2+ with cadmium(II) during core assembly. Cd2+ inhibits the yield of reconstitution of O2-evolution activity, called photoactivation, starting from the free inorganic cofactors and the cofactor-depleted apo-WOC-PSII complex. Ca2+ affinity increases following photooxidation of the first Mn2+ to Mn3+ bound to the 'high-affinity' site. Ca2+ binding occurs in the dark and is the slowest overall step of photoactivation (IM1→IM 1* step). Cd2+ competitively blocks the binding of Ca2+ to its functional site with 10- to 30-fold higher affinity, but does not influence the binding of Mn2+ to its high-affinity site. By contrast, even 10-fold higher concentrations of Cd2+ have no effect on O2-evolution activity in intact PSII-WOC. Paradoxically, Cd 2+ both inhibits photoactivation yield, while accelerating the rate of photoassembly of active centres 10-fold relative to Ca2+. Cd 2+ increases the kinetic stability of the photooxidized Mn 3+ assembly intermediate(s) by twofold (mean lifetime for dark decay). The rate data provide evidence that Cd2+ binding following photooxidation of the first Mn3+, IM1→IM 1*, causes three outcomes: (i) a longer intermediate lifetime that slows IM1 decay to IM0 by charge recombination, (ii) 10-fold higher probability of attaining the degrees of freedom (either or both cofactor and protein d.f.) needed to bind and photooxidize the remaining 3 Mn2+ that form the functional cluster, and (iii) increased lability of Cd2+ following Mn4 cluster assembly results in (re)exchange of Cd2+ by Ca2+ which restores active O2-evolving centres. Prior EPR spectroscopic data provide evidence for an oxo-bridged assembly intermediate, Mn 3+(μ-O2-)Ca2+, for IM1*. We postulate an analogous inhibited intermediate with Cd2+ replacing Ca2+.
KW - Calcium
KW - Manganese
KW - Oxygen evolution
KW - Photosynthesis
KW - Photosystem II
KW - Water oxidation
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U2 - 10.1098/rstb.2007.2222
DO - 10.1098/rstb.2007.2222
M3 - Article
VL - 363
SP - 1253
EP - 1261
JO - Philosophical Transactions of the Royal Society B: Biological Sciences
JF - Philosophical Transactions of the Royal Society B: Biological Sciences
SN - 0962-8436
IS - 1494
ER -