X-Ray Damage to the Mn4Ca Complex in Single Crystals of Photosystem II: A Case Study for Metalloprotein Crystallography

X-ray absorption spectroscopy was used to measure the damage caused by exposure to x-rays to the Mn4Ca active site in single crystals of photosystem II as a function of dose and energy of x-rays, temperature, and time. These studies reveal that the conditions used for structure determination by x-ra...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2005-08, Vol.102 (34), p.12047-12052
Main Authors: Yano, Junko, Kern, Jan, Irrgang, Klaus-Dieter, Latimer, Matthew J, Bergmann, Uwe, Glatzel, Pieter, Pushkar, Yulia, Biesiadka, Jacek, Loll, Bernhard, Sauer, Kenneth, Messinger, Johannes, Zouni, Athina, Yachandra, Vittal K
Format: Article
Language:English
Subjects:
Biological Sciences
Calcium - chemistry
Crystallography
Crystals
Cyanobacteria - chemistry
Dosage
Dose-Response Relationship, Radiation
Flood damage
Manganese Compounds - chemistry
Manganese Compounds - radiation effects
Metalloproteins - chemistry
Photons
Photosystem II Protein Complex - chemistry
Radiation damage
Radiation dosage
Single crystals
Spectrum Analysis
Temperature
Time Factors
Wave diffraction
X ray spectrum
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Summary:X-ray absorption spectroscopy was used to measure the damage caused by exposure to x-rays to the Mn4Ca active site in single crystals of photosystem II as a function of dose and energy of x-rays, temperature, and time. These studies reveal that the conditions used for structure determination by x-ray crystallography cause serious damage specifically to the metal-site structure. The x-ray absorption spectra show that the structure changes from one that is characteristic of a high-valent Mn4( III2, IV2) oxo-bridged Mn4Ca cluster to that of Mn(II) in aqueous solution. This damage to the metal site occurs at a dose that is more than one order of magnitude lower than the dose that results in loss of diffractivity and is commonly considered safe for protein crystallography. These results establish quantitative x-ray dose parameters that are applicable to redox-active metalloproteins. This case study shows that a careful evaluation of the structural intactness of the active site(s) by spectroscopic techniques can validate structures derived from crystallography and that it can be a valuable complementary method before structure-function correlations of metalloproteins can be made on the basis of high-resolution x-ray crystal structures.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0505207102