title: Ligation of D1-His332 and D1-Asp170 to the manganese cluster of photosystem II from Synechocystis assessed by multifrequency pulse EPR spectroscopy.
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.
authors.affiliation: Department of Chemistry, University of California at Davis, Davis, California 95616, United States.
authors.forename: Troy A
authors.initials: TA
authors.lastname: Stich
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Yeagle
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Service
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Debus
authors.forename: R David
authors.initials: RD
authors.lastname: Britt
mesh_terms: D001224:Aspartic Acid / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006639:Histidine / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics
chemical_list: D045332:Photosystem II Protein Complex; D001224:Aspartic Acid; D008345:Manganese; D006639:Histidine; D010100:Oxygen