The Manganese Complex of Photosystem II: Extended-Range EXAFS Data and Specific Structural Models for Four S-States
The water-oxidizing manganese complex bound to the proteins of photosystem II (PSII) was studied by X-ray absorption spectroscopy on PSII membrane particles. An extended range for collection of EXAFS data was used (up to 16.6 Å−1). The EXAFS suggests the presence of two Mn-Mn distances close to 2.7 Å (per Mn4Ca complex); the existence of a third Mn-Mn distance below 2.9 Å is not indicated by the EXAFS data. A distance of 3.7 Å is clearly resolved in the extended-range data and tentatively assigned to a Mn-Mn distance. Taking into account the above EXAFS results (inter alia), we present a model for the structure of the PSII manganese complex, which differs from previous atomic-resolution models. Emphasizing the hypothetical character, we propose for all semi-stable S-states (i) a structure of the Mn4Ca(μ-O)n core, (ii) a model of the amino-acid environment, and (iii) assignments of distinct Mn oxidation states to the individual Mn ions. This specific working model may permit discussion, verification, and invalidation of its various features by comparison with experimental and theoretical findings.
KeywordsEXAFS manganese complex oxygen evolution Photosystem II S-states X-ray absorption spectroscopy
Unable to display preview. Download preview PDF.
- Dau H, Haumann M (2006) Reaction cycle of photosynthetic water oxidation in plants and cyanobacteria. Science 312:1471-1472.Google Scholar
- Dau H, Liebisch P, Haumann M (2003) X-ray absorption spectroscopy to analyze nuclear geometry and electronic structure of biological metal centers - potential and questions examined with special focus on the tetranuclear manganese complex of oxygenic photosynthesis. Anal Bioanal Chem 376:562-583.PubMedCrossRefGoogle Scholar
- Dau H, Grundmeier A, Loja P, Haumann M (2007) On the structure of the manganese complex of photosystem II - extended-range EXAFS data an specific atomic resolution models for four S-states. Phil Trans R Soc B 363 (doi:10.1098/rstb.2007.2220).Google Scholar
- Haumann M, Muller C, Liebisch P, Iuzzolino L, Dittmer J, Grabolle M, Neisius T, Meyer-Klaucke W, Dau H (2005) Structural and oxidation state changes of the photosystem II manganese complex in four transitions of the water oxidation cycle (S0 → S1, S1 → S2, S2 → S3, and S3,4 → S0) characterized by X-ray absorption spectroscopy at 20 K and room temperature. Biochemistry 44:1894-1908.PubMedCrossRefGoogle Scholar
- Yano J, Kern J, Irrgang K-D, Latimer MJ, Bergmann U, Glatzel P, Pushkar Y, Biesiadka J, Loll B, Sauer K, Messinger J, Zouni A, Yachandra VK (2005a) X-ray damage to the Mn4Ca complex in single crystals of photosystem II: A case study for metalloprotein crystal-lography. Proc Natl Acad Sci USA 102:12047-12052.PubMedCrossRefGoogle Scholar