A new milestone for photosynthesis

A new milestone for photosynthesis The photosynthetic water-splitting reaction catalysed by the oxygen-evolving center (OEC) in the photosystem II of plants releases protons, electrons and dioxygen, which is one of the most important processes for energy and material conversions on Earth. OEC is a Mn4Ca-cluster and cycles through five different states (Sn, n = 0–4), wherein S0 is the most reduced state, S1 is the dark stable state and S2, S3 and S4 are intermediate states. OEC rapidly releases O2 in the S4 state, then returns to the S0 state. The detailed structure of the OEC in the S1 state was reported by Umena et al. in 2011 [1] and improved by Suga et al. in 2015 [2]. These reports from Shen's group have revealed that OEC is composed of an asymmetric Mn4CaO5-cluster coordinated by four water molecules, one imidazole and six carboxylate groups from protein side chains (Fig. 1). Determination of the accurate structure of the OEC in the S1 state [1,2] is a breakthrough in the field of photosynthesis. However, because of the complexities of the large protein environment and the dynamic changes of the OEC during the water-splitting reaction, it is a great challenge to reveal its detailed reaction mechanism. Figure 1. View largeDownload slide Structures of OEC in the S1 and S3 states. Figure 1. View largeDownload slide Structures of OEC in the S1 and S3 states. Recently, Shen's group reached a new milestone [3]. They reported the structure of the S3 intermediate state OEC by using time-resolved serial femtosecond X-ray crystallography with an X-ray free electron laser [3], which, for the first time, identified the formation of the O–O bond between the ‘famous’ μ4-O5 and a newly inserted oxygen atom (O6) with a length of 1.5 Å (Fig. 1). The O=O bond formation is key to understanding the mechanism of the photosynthetic water-splitting reaction, which has attracted the extensive attention of various spectroscopic and theoretical studies during the last several decades [4]. A recent breakthrough from Shen's group has provided unambiguous evidence for the crucial O–O bond formation [3]; meanwhile, new questions arise for future studies. For example, how is the O6 atom inserted into the OEC? What are the functional roles of the four water molecules coordinated to the OEC, and what is the real function of the μ2-O4 atom? Finally, what is the structure of the OEC in the S4 state? According to the binding mode of the O–O bond in the S3 state, the release of O2 in the S4 state would produce four reactive sites, namely three 5-coordinated manganese (i.e. Mn1, Mn3, Mn4) and one 6-coordinated calcium. Based on our knowledge from an artificial Mn4CaO4-cluster [5], significant structural rearrangements would occur to accommodate the newly formed Mn4CaO4-cluster. In summary, the previous outstanding achievements by Shen's group revealed the accurate structures of the OEC in the S1 state [1,2], which was already considered to be a breakthrough in photosynthesis. The recent finding on the mechanism of O–O bond formation [3] is a new milestone for photosynthetic research. These achievements have contributed to enhancing our knowledge on photosynthetic oxygen evolution tremendously, and will significantly promote the development of the new generation of man-made OEC for water-splitting reactions in artificial photosynthesis, aiming to produce clean and renewable fuels from sunlight and water. REFERENCES 1. Umena Y , Kawakami K , Shen JR et al. Nature 2011 ; 473 : 55 – 60 . 2. Suga M , Akita F , Hirata K et al. Nature 2015 ; 517 : 99 – 103 . 3. Suga M , Akita F , Sugahara M et al. Nature 2017 ; 543 : 131 – 5 . 4. Perez-Navarro M , Neese F , Lubitz W et al. Curr Opin Chem Biol 2016 ; 31 : 113 – 9 . 5. Zhang C , Chen C , Dong H et al. Science 2015 ; 348 : 690 – 3 . © The Author(s) 2017. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png National Science Review Oxford University Press

A new milestone for photosynthesis

Loading next page...
 
/lp/ou_press/a-new-milestone-for-photosynthesis-YniUYEm2FY
Publisher
Oxford University Press
Copyright
© The Author(s) 2017. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd.
ISSN
2095-5138
eISSN
2053-714X
D.O.I.
10.1093/nsr/nwx087
Publisher site
See Article on Publisher Site

Abstract

The photosynthetic water-splitting reaction catalysed by the oxygen-evolving center (OEC) in the photosystem II of plants releases protons, electrons and dioxygen, which is one of the most important processes for energy and material conversions on Earth. OEC is a Mn4Ca-cluster and cycles through five different states (Sn, n = 0–4), wherein S0 is the most reduced state, S1 is the dark stable state and S2, S3 and S4 are intermediate states. OEC rapidly releases O2 in the S4 state, then returns to the S0 state. The detailed structure of the OEC in the S1 state was reported by Umena et al. in 2011 [1] and improved by Suga et al. in 2015 [2]. These reports from Shen's group have revealed that OEC is composed of an asymmetric Mn4CaO5-cluster coordinated by four water molecules, one imidazole and six carboxylate groups from protein side chains (Fig. 1). Determination of the accurate structure of the OEC in the S1 state [1,2] is a breakthrough in the field of photosynthesis. However, because of the complexities of the large protein environment and the dynamic changes of the OEC during the water-splitting reaction, it is a great challenge to reveal its detailed reaction mechanism. Figure 1. View largeDownload slide Structures of OEC in the S1 and S3 states. Figure 1. View largeDownload slide Structures of OEC in the S1 and S3 states. Recently, Shen's group reached a new milestone [3]. They reported the structure of the S3 intermediate state OEC by using time-resolved serial femtosecond X-ray crystallography with an X-ray free electron laser [3], which, for the first time, identified the formation of the O–O bond between the ‘famous’ μ4-O5 and a newly inserted oxygen atom (O6) with a length of 1.5 Å (Fig. 1). The O=O bond formation is key to understanding the mechanism of the photosynthetic water-splitting reaction, which has attracted the extensive attention of various spectroscopic and theoretical studies during the last several decades [4]. A recent breakthrough from Shen's group has provided unambiguous evidence for the crucial O–O bond formation [3]; meanwhile, new questions arise for future studies. For example, how is the O6 atom inserted into the OEC? What are the functional roles of the four water molecules coordinated to the OEC, and what is the real function of the μ2-O4 atom? Finally, what is the structure of the OEC in the S4 state? According to the binding mode of the O–O bond in the S3 state, the release of O2 in the S4 state would produce four reactive sites, namely three 5-coordinated manganese (i.e. Mn1, Mn3, Mn4) and one 6-coordinated calcium. Based on our knowledge from an artificial Mn4CaO4-cluster [5], significant structural rearrangements would occur to accommodate the newly formed Mn4CaO4-cluster. In summary, the previous outstanding achievements by Shen's group revealed the accurate structures of the OEC in the S1 state [1,2], which was already considered to be a breakthrough in photosynthesis. The recent finding on the mechanism of O–O bond formation [3] is a new milestone for photosynthetic research. These achievements have contributed to enhancing our knowledge on photosynthetic oxygen evolution tremendously, and will significantly promote the development of the new generation of man-made OEC for water-splitting reactions in artificial photosynthesis, aiming to produce clean and renewable fuels from sunlight and water. REFERENCES 1. Umena Y , Kawakami K , Shen JR et al. Nature 2011 ; 473 : 55 – 60 . 2. Suga M , Akita F , Hirata K et al. Nature 2015 ; 517 : 99 – 103 . 3. Suga M , Akita F , Sugahara M et al. Nature 2017 ; 543 : 131 – 5 . 4. Perez-Navarro M , Neese F , Lubitz W et al. Curr Opin Chem Biol 2016 ; 31 : 113 – 9 . 5. Zhang C , Chen C , Dong H et al. Science 2015 ; 348 : 690 – 3 . © The Author(s) 2017. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

National Science ReviewOxford University Press

Published: Jul 1, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off