1. Ligation of D1-His332 and D1-Asp170 to the manganese cluster of photosystem II from Synechocystis assessed by multifrequency pulse EPR spectroscopy.
- Author
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Stich TA, Yeagle GJ, Service RJ, Debus RJ, and Britt RD
- Subjects
- Models, Molecular, Mutagenesis, Site-Directed, Mutation, Oxygen metabolism, Photosystem II Protein Complex genetics, Protein Conformation, Synechocystis genetics, Aspartic Acid metabolism, Electron Spin Resonance Spectroscopy methods, Histidine metabolism, Manganese metabolism, Photosystem II Protein Complex chemistry, Photosystem II Protein Complex metabolism, Synechocystis enzymology
- Abstract
Multifrequency electron spin-echo envelope modulation (ESEEM) spectroscopy is used to ascertain the nature of the bonding interactions of various active site amino acids with the Mn ions that compose the oxygen-evolving cluster (OEC) in photosystem II (PSII) from the cyanobacterium Synechocystis sp. PCC 6803 poised in the S(2) state. Spectra of natural isotopic abundance PSII ((14)N-PSII), uniformly (15)N-labeled PSII ((15)N-PSII), and (15)N-PSII containing (14)N-histidine ((14)N-His/(15)N-PSII) are compared. These complementary data sets allow for a precise determination of the spin Hamiltonian parameters of the postulated histidine nitrogen interaction with the Mn ions of the OEC. These results are compared to those from a similar study on PSII isolated from spinach. Upon mutation of His332 of the D1 polypeptide to a glutamate residue, all isotopically sensitive spectral features vanish. Additional K(a)- and Q-band ESEEM experiments on the D1-D170H site-directed mutant give no indication of new (14)N-based interactions.
- Published
- 2011
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