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Updated: Aug 15, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Identification of histidine at the catalytic site of the photosynthetic oxygen-evolving complex
X S Tang1, B A Diner, B S Larsen
1Central Research and Development Department, Experimental Station, E.I. Dupont de Nemours and Company, Wilmington, DE 19880.
Abstract:
The molecular oxygen in our atmosphere is a product of a water-splitting reaction that occurs in the oxygen-evolving complex of photosystem II of oxygenic photosynthesis. The catalytic core of the oxygen-evolving complex is an ensemble of four manganese atoms arranged in a cluster of undetermined structure. The pulsed electron paramagnetic resonance (EPR) technique of electron spin-echo envelope modulation (ESEEM) can be used to measure nuclear spin transitions of nuclei magnetically coupled to paramagnetic metal centers of enzymes. We report the results of ESEEM experiments on the cyanobacterium Synechocystis PCC 6803 selectively labeled with 15N at the two nitrogen sites of the imidazole side chain of histidine residues. The experiments demonstrate that histidine is bound to manganese in the oxygen-evolving complex.
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