Abstract
Herein we extend prior studies of biosynthetic strontium replacement of calcium in PSII-WOC core particles to characterize whole cells. Previous studies of Thermosynechococcus elongatus found a lower rate of light-saturated O2 from isolated PSII-WOC(Sr) cores and 5-8 × slower rate of oxygen release. We find similar properties in whole cells, and show it is due to a 20% larger Arrhenius activation barrier for O2 evolution. Cellular adaptation to the sluggish PSII-WOC(Sr) cycle occurs in which flux through the QAQB acceptor gate becomes limiting for turnover rate in vivo. Benzoquinone derivatives that bind to QB site remove this kinetic chokepoint yielding 31% greater O2 quantum yield (QY) of PSII-WOC(Sr) vs. PSII-WOC(Ca). QY and efficiency of the WOC(Sr) catalytic cycle are greatly improved at low light flux, due to fewer misses and backward transitions and 3-fold longer lifetime of the unstable S3 state, attributed to greater thermodynamic stabilization of the WOC(Sr) relative to the photoactive tyrosine YZ. More linear and less cyclic electron flow through PSII occurs per PSII-WOC(Sr). The organismal response to the more active PSII centers in Sr-grown cells at 45 °C is to lower the number of active PSII-WOC per Chl, producing comparable oxygen and energy per cell. We conclude that redox and protonic energy fluxes created by PSII are primary determinants for optimal growth rate of T. elongatus. We further conclude that the (Sr-favored) intermediate-spin S = 5/2 form of the S2 state is the active form in the catalytic cycle relative to the low-spin S = 1/2 form.
| Original language | English |
|---|---|
| Pages (from-to) | 1550-1560 |
| Number of pages | 11 |
| Journal | Biochimica et Biophysica Acta - Bioenergetics |
| Volume | 1857 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - Sep 1 2016 |
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Keywords
- Manganese
- Oxygen
- Photosystem II
- Strontium
- Thermosynechococcus
- Water oxidizing complex
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Cell Biology
Cite this
The strontium inorganic mutant of the water oxidizing center (CaMn4O5) of PSII improves WOC efficiency but slows electron flux through the terminal acceptors. / Gates, Colin; Ananyev, Gennady; Dismukes, G Charles.
In: Biochimica et Biophysica Acta - Bioenergetics, Vol. 1857, No. 9, 01.09.2016, p. 1550-1560.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The strontium inorganic mutant of the water oxidizing center (CaMn4O5) of PSII improves WOC efficiency but slows electron flux through the terminal acceptors
AU - Gates, Colin
AU - Ananyev, Gennady
AU - Dismukes, G Charles
PY - 2016/9/1
Y1 - 2016/9/1
N2 - Herein we extend prior studies of biosynthetic strontium replacement of calcium in PSII-WOC core particles to characterize whole cells. Previous studies of Thermosynechococcus elongatus found a lower rate of light-saturated O2 from isolated PSII-WOC(Sr) cores and 5-8 × slower rate of oxygen release. We find similar properties in whole cells, and show it is due to a 20% larger Arrhenius activation barrier for O2 evolution. Cellular adaptation to the sluggish PSII-WOC(Sr) cycle occurs in which flux through the QAQB acceptor gate becomes limiting for turnover rate in vivo. Benzoquinone derivatives that bind to QB site remove this kinetic chokepoint yielding 31% greater O2 quantum yield (QY) of PSII-WOC(Sr) vs. PSII-WOC(Ca). QY and efficiency of the WOC(Sr) catalytic cycle are greatly improved at low light flux, due to fewer misses and backward transitions and 3-fold longer lifetime of the unstable S3 state, attributed to greater thermodynamic stabilization of the WOC(Sr) relative to the photoactive tyrosine YZ. More linear and less cyclic electron flow through PSII occurs per PSII-WOC(Sr). The organismal response to the more active PSII centers in Sr-grown cells at 45 °C is to lower the number of active PSII-WOC per Chl, producing comparable oxygen and energy per cell. We conclude that redox and protonic energy fluxes created by PSII are primary determinants for optimal growth rate of T. elongatus. We further conclude that the (Sr-favored) intermediate-spin S = 5/2 form of the S2 state is the active form in the catalytic cycle relative to the low-spin S = 1/2 form.
AB - Herein we extend prior studies of biosynthetic strontium replacement of calcium in PSII-WOC core particles to characterize whole cells. Previous studies of Thermosynechococcus elongatus found a lower rate of light-saturated O2 from isolated PSII-WOC(Sr) cores and 5-8 × slower rate of oxygen release. We find similar properties in whole cells, and show it is due to a 20% larger Arrhenius activation barrier for O2 evolution. Cellular adaptation to the sluggish PSII-WOC(Sr) cycle occurs in which flux through the QAQB acceptor gate becomes limiting for turnover rate in vivo. Benzoquinone derivatives that bind to QB site remove this kinetic chokepoint yielding 31% greater O2 quantum yield (QY) of PSII-WOC(Sr) vs. PSII-WOC(Ca). QY and efficiency of the WOC(Sr) catalytic cycle are greatly improved at low light flux, due to fewer misses and backward transitions and 3-fold longer lifetime of the unstable S3 state, attributed to greater thermodynamic stabilization of the WOC(Sr) relative to the photoactive tyrosine YZ. More linear and less cyclic electron flow through PSII occurs per PSII-WOC(Sr). The organismal response to the more active PSII centers in Sr-grown cells at 45 °C is to lower the number of active PSII-WOC per Chl, producing comparable oxygen and energy per cell. We conclude that redox and protonic energy fluxes created by PSII are primary determinants for optimal growth rate of T. elongatus. We further conclude that the (Sr-favored) intermediate-spin S = 5/2 form of the S2 state is the active form in the catalytic cycle relative to the low-spin S = 1/2 form.
KW - Manganese
KW - Oxygen
KW - Photosystem II
KW - Strontium
KW - Thermosynechococcus
KW - Water oxidizing complex
UR - http://www.scopus.com/inward/record.url?scp=84975797424&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84975797424&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2016.06.004
DO - 10.1016/j.bbabio.2016.06.004
M3 - Article
VL - 1857
SP - 1550
EP - 1560
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 9
ER -