Metalloproteins containing manganese in a redox-active role are involved in a variety of physiologically important reactions of dioxygen metabolism. These include, amongst others, a superoxide dismutase that detoxifies superoxide radicals to O2 and peroxide, a catalase that disproportionates peroxide to O2 and H2O, and perhaps the most complex and important, the Mn-containing oxygen-evolving complex (Mn-OEC) that is involved in the oxidation of water to dioxygen in photosystem II. The Mn-OEC generates almost all of the dioxygen that supports aerobic life, and it is abundant in the atmosphere because of its constant regeneration by the oxidation of water. The light-induced oxidation of water to dioxygen is one of the most important chemical processes occurring on such a large scale in the biosphere. The water-oxidation reaction involves removal of four electrons, in a stepwise manner by light-induced oxidation, from two water molecules by the Mn-OEC to produce a molecule of oxygen. Central questions that need to be resolved and the overall objective of this proposal are as follows: 1) Characterize the structure and the changes of the oxo-bridged heteronuclear Mn4Ca complex as it advances through the enzymatic cycle, 2) Elucidate the structural and functional role of the cofactors Cl- and Ca2+, 3) Determine the oxidation states and electronic structure of the Mn complex in the four intermediate S-states, 4) Determine the mechanism of water oxidation and oxygen evolution. The interplay between X-ray spectroscopy and EPR has played an essential role in our understanding of the structural and mechanistic aspects of O2 evolution. The samples for X-ray spectroscopy will be characterized by EPR. The structural changes of the Mn complex as it advances through the enzymatic cycle are determined by high-resolution XAS methods using samples prepared by flash illumination, and single- crystals of PS II. The oxidation states and electronic structure of the Mn complex are determined by Mn K- and L-edge, K? emission, and X-ray resonant Raman spectroscopies.

Public Health Relevance

Several manganese enzymes are involved in the process of oxygen metabolism, and one of the most complicated and least understood is the multinuclear manganese cluster in the oxygen-evolving complex, which is the only enzyme that is capable of generating O2 from H2O. This proposal is directed towards the determination of the structure and mechanism of this critically important manganese enzyme.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM055302-15
Application #
8333425
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Anderson, Vernon
Project Start
1997-01-01
Project End
2014-08-31
Budget Start
2012-09-01
Budget End
2013-08-31
Support Year
15
Fiscal Year
2012
Total Cost
$481,000
Indirect Cost
$206,190
Name
Lawrence Berkeley National Laboratory
Department
Other Basic Sciences
Type
Organized Research Units
DUNS #
078576738
City
Berkeley
State
CA
Country
United States
Zip Code
94720
Hattne, Johan; Echols, Nathaniel; Tran, Rosalie et al. (2014) Accurate macromolecular structures using minimal measurements from X-ray free-electron lasers. Nat Methods 11:545-8
Glockner, Carina; Kern, Jan; Broser, Matthias et al. (2013) Structural changes of the oxygen-evolving complex in photosystem II during the catalytic cycle. J Biol Chem 288:22607-20
Glatzel, Pieter; Schroeder, Henning; Pushkar, Yulia et al. (2013) Electronic structural changes of Mn in the oxygen-evolving complex of photosystem II during the catalytic cycle. Inorg Chem 52:5642-4
Lassalle-Kaiser, Benedikt; Boron 3rd, Thaddeus T; Krewald, Vera et al. (2013) Experimental and computational X-ray emission spectroscopy as a direct probe of protonation states in oxo-bridged Mn(IV) dimers relevant to redox-active metalloproteins. Inorg Chem 52:12915-22
Krewald, Vera; Lassalle-Kaiser, Benedikt; Boron 3rd, Thaddeus T et al. (2013) The protonation states of oxo-bridged Mn(IV) dimers resolved by experimental and computational Mn K pre-edge X-ray absorption spectroscopy. Inorg Chem 52:12904-14
Smolentsev, Grigory; Soldatov, Alexander V; Messinger, Johannes et al. (2009) X-ray emission spectroscopy to study ligand valence orbitals in Mn coordination complexes. J Am Chem Soc 131:13161-7
Yano, Junko; Kern, Jan; Pushkar, Yulia et al. (2008) High-resolution structure of the photosynthetic Mn4Ca catalyst from X-ray spectroscopy. Philos Trans R Soc Lond B Biol Sci 363:1139-47;discussion 1147
Pushkar, Yulia; Yano, Junko; Sauer, Kenneth et al. (2008) Structural changes in the Mn4Ca cluster and the mechanism of photosynthetic water splitting. Proc Natl Acad Sci U S A 105:1879-84
Sauer, Kenneth; Yano, Junko; Yachandra, Vittal K (2008) X-Ray spectroscopy of the photosynthetic oxygen-evolving complex. Coord Chem Rev 252:318-335
Yano, Junko; Yachandra, Vittal K (2007) Oxidation state changes of the Mn4Ca cluster in photosystem II. Photosynth Res 92:289-303

Showing the most recent 10 out of 31 publications