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15 N HYSCORE Characterization of the Fully Deprotonated, Reduced Form of the Archaeal Rieske [2Fe−2S] Center

2006; American Chemical Society; Volume: 128; Issue: 7 Linguagem: Inglês

10.1021/ja0562393

1943-2984

Toshio Iwasaki, Asako Kounosu, Rimma I. Samoilova, Sergei A. Dikanov,

Metalloenzymes and iron-sulfur proteins

The hyperfine couplings for strongly and weakly coupled 15N nuclei around a reduced Rieske [2Fe−2S] center of uniformly 15N-labeled, hyperthermostable archaeal Rieske protein at pH 13.3 were determined by hyperfine sublevel correlation (HYSCORE) spectroscopy and compared with those at physiological pH. Significant changes in the hyperfine couplings of the terminal histidine Nδ ligands and Nε nuclei were observed between them, which can be explained by not only the redistribution of the unpaired electron spin density over the ligands but also the difference in the mixed-valence state of the fully deprotonated, reduced cluster. These quantitative data can be used in theoretical analysis for the selection of an appropriate model of the mixed-valence state of the reduced Rieske center at very alkaline pH.