TY - JOUR
T1 - Why Did Nature Choose Manganese over Cobalt to Make Oxygen Photosynthetically on the Earth?
AU - Gates, Colin
AU - Ananyev, Gennady
AU - Roy-Chowdhury, Shatabdi
AU - Cullinane, Brendan
AU - Miller, Mathias
AU - Fromme, Petra
AU - Dismukes, G. Charles
N1 - Funding Information:
We thank Prof. Gene Hall for the use of ICP-OES equipment and Shivam Kaushik for preliminary experiments. This work was supported by the US Department of Energy Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences Photosynthetic Systems grant DE-SC0019460. We thank Paul Smith and Yulia Pushkar for comments and a preprint.
Funding Information:
We thank Prof. Gene Hall for the use of ICP-OES equipment and Shivam Kaushik for preliminary experiments. This work was supported by the US Department of Energy Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, Photosynthetic Systems grant DE-SC0019460. We thank Paul Smith and Yulia Pushkar for comments and a preprint.
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/5/5
Y1 - 2022/5/5
N2 - All contemporary oxygenic phototrophs─from primitive cyanobacteria to complex multicellular plants─split water using a single invariant cluster comprising Mn4CaO5(the water oxidation catalyst) as the catalyst within photosystem II, the universal oxygenic reaction center of natural photosynthesis. This cluster is unstable outside of PSII and can be reconstituted, both in vivo and in vitro, using elemental aqueous ions and light, via photoassembly. Here, we demonstrate the first functional substitution of manganese in any oxygenic reaction center by in vitro photoassembly. Following complete removal of inorganic cofactors from cyanobacterial photosystem II microcrystal (PSIIX), photoassembly with free cobalt (Co2+), calcium (Ca2+), and water (OH-) restores O2evolution activity. Photoassembly occurs at least threefold faster using Co2+versus Mn2+due to a higher quantum yield for PSIIX-mediated charge separation (P*): Co2+→ P∗ → Co3+QA-. However, this kinetic preference for Co2+over native Mn2+during photoassembly is offset by significantly poorer catalytic activity (∼25% of the activity with Mn2+) and ∼3- to 30-fold faster photoinactivation rate. The resulting reconstituted Co-PSIIX oxidizes water by the standard four-flash photocycle, although they produce 4-fold less O2per PSII, suggested to arise from faster charge recombination (Co3+QA← Co4+QA-) in the catalytic cycle. The faster photoinactivation of reconstituted Co-PSIIX occurs under anaerobic conditions during the catalytic cycle, suggesting direct photodamage without the involvement of O2. Manganese offers two advantages for oxygenic phototrophs, which may explain its exclusive retention throughout Darwinian evolution: significantly slower charge recombination (Mn3+QA← Mn4+QA-) permits more water oxidation at low and fluctuating solar irradiation (greater net energy conversion) and much greater tolerance to photodamage at high light intensities (Mn4+is less oxidizing than Co4+). Future work to identify the chemical nature of the intermediates will be needed for further interpretation.
AB - All contemporary oxygenic phototrophs─from primitive cyanobacteria to complex multicellular plants─split water using a single invariant cluster comprising Mn4CaO5(the water oxidation catalyst) as the catalyst within photosystem II, the universal oxygenic reaction center of natural photosynthesis. This cluster is unstable outside of PSII and can be reconstituted, both in vivo and in vitro, using elemental aqueous ions and light, via photoassembly. Here, we demonstrate the first functional substitution of manganese in any oxygenic reaction center by in vitro photoassembly. Following complete removal of inorganic cofactors from cyanobacterial photosystem II microcrystal (PSIIX), photoassembly with free cobalt (Co2+), calcium (Ca2+), and water (OH-) restores O2evolution activity. Photoassembly occurs at least threefold faster using Co2+versus Mn2+due to a higher quantum yield for PSIIX-mediated charge separation (P*): Co2+→ P∗ → Co3+QA-. However, this kinetic preference for Co2+over native Mn2+during photoassembly is offset by significantly poorer catalytic activity (∼25% of the activity with Mn2+) and ∼3- to 30-fold faster photoinactivation rate. The resulting reconstituted Co-PSIIX oxidizes water by the standard four-flash photocycle, although they produce 4-fold less O2per PSII, suggested to arise from faster charge recombination (Co3+QA← Co4+QA-) in the catalytic cycle. The faster photoinactivation of reconstituted Co-PSIIX occurs under anaerobic conditions during the catalytic cycle, suggesting direct photodamage without the involvement of O2. Manganese offers two advantages for oxygenic phototrophs, which may explain its exclusive retention throughout Darwinian evolution: significantly slower charge recombination (Mn3+QA← Mn4+QA-) permits more water oxidation at low and fluctuating solar irradiation (greater net energy conversion) and much greater tolerance to photodamage at high light intensities (Mn4+is less oxidizing than Co4+). Future work to identify the chemical nature of the intermediates will be needed for further interpretation.
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U2 - 10.1021/acs.jpcb.2c00749
DO - 10.1021/acs.jpcb.2c00749
M3 - Article
C2 - 35446582
AN - SCOPUS:85129297387
SN - 1520-6106
VL - 126
SP - 3257
EP - 3268
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 17
ER -