Dependence of the proton magnetic resonance spectra on the oxidation state of flavodoxin from Clostridium MP and from Peptostreptococcus elsdenii.
نویسندگان
چکیده
The broadening of protein nuclear magnetic resonances in the spectra of the semiquinone forms of flavodoxins derived from Clostridium MP and Peptostreptococcus elsdenii relative to the resonances in the oxidized and reduced forms is highly selective. Spectra from both species of flavodoxin indicate that conformational differences between the oxidized and fully reduced states are minor and, consequently, the broadening in the semiquinone form is ascribed to the paramagnetic effect of the flavin free radical. The chemical shifts of the paramagnetically broadened lines are used in conjunction with x-ray crystallographic models to assign peaks to amino-acid residues in the proximity of the flavin mononucleotide. Species-dependent differences in the spectra can generally be attributed to differences in amino-acid composition and sequence. The spectra from both species of flavodoxin indicate that there is slow exchange between oxidized and semiquinone forms or reduced and semiquinone forms of the flavodoxins with a limit of k(ex) < 50 sec(-1) for the exchange rate.
منابع مشابه
Bba 66291 Studies on Flavin Binding in Flavodoxins
I. Stable apoproteins have been prepared from Peptostreptococcus elsdenii, C. pasteurianum and Clostridium MP flavodoxins by dialysis of the native proteins against 2 M KBr at pH 3.9 and 3" lO-4 M EDTA. The apoproteins each bind I molecule of FMN to give complexes identical with the native flavodoxins. 2. Binding causes almost complete quenching of both protein and FMN fluorescence. This proper...
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عنوان ژورنال:
- Proceedings of the National Academy of Sciences of the United States of America
دوره 70 12 شماره
صفحات -
تاریخ انتشار 1973