The high-potential iron protein (HiPIP) from Clostridium uinosum has been reconstituted with a [Fe4Se4] cluster. The modified protein has a reduction potential of 321 (7) mV vs NHE [p 0.1 M phosphate; pH 7.0; 23 "C]. The upfield and downfield isotropically shifted resonances in the 'H NMR spectra of both the oxidized and reduced proteins are assigned to P-CH, protons of coordinating cysteine residues and to neighboring aromatics. The variable-temperature behavior of each of these resonances is reported. Unlike the 2[Fe4Se4]Fd's from C. pasteurianum and C. acidi-urici, no evidence was found for the involvement of higher spin states. HiPIP self-exchange electron-transfer rate constants have been estimated from TI measurements: native, 1.7 (4) X lo4; Se-modified, 7 (2) X lo4 M-' s-l [p 0.1 M phosphate; pH 7.0 (D20); 25 "C].
1H NMR spectra and electron transfer properties of oxidized and reduced Fe4Se4 derivative of chromatium vinosum high-potential iron protein / Sola, Marco; J. A., Cowan; H. B., Gray. - In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - ISSN 0002-7863. - STAMPA. - 111:(1989), pp. 6627-6630.
1H NMR spectra and electron transfer properties of oxidized and reduced Fe4Se4 derivative of chromatium vinosum high-potential iron protein
SOLA, Marco;
1989-01-01
Abstract
The high-potential iron protein (HiPIP) from Clostridium uinosum has been reconstituted with a [Fe4Se4] cluster. The modified protein has a reduction potential of 321 (7) mV vs NHE [p 0.1 M phosphate; pH 7.0; 23 "C]. The upfield and downfield isotropically shifted resonances in the 'H NMR spectra of both the oxidized and reduced proteins are assigned to P-CH, protons of coordinating cysteine residues and to neighboring aromatics. The variable-temperature behavior of each of these resonances is reported. Unlike the 2[Fe4Se4]Fd's from C. pasteurianum and C. acidi-urici, no evidence was found for the involvement of higher spin states. HiPIP self-exchange electron-transfer rate constants have been estimated from TI measurements: native, 1.7 (4) X lo4; Se-modified, 7 (2) X lo4 M-' s-l [p 0.1 M phosphate; pH 7.0 (D20); 25 "C].
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