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The CD spectra and thermodynamic properties of the iron protein of nitrogenase from N_(2)-and NH~(+)_(4)-grown Alcaligenes faecalis

Hai Weili, Song Wei, You Chongbiao, Li Zhong, Wang Wenqing

Institute for Application of Atomic Energy, CAAS. Beijing；China(100871)

Abstract

The purified iron proteins(Af2 and Af*2)of nitrogenase from Alcaligenes faecalis strain A1501 cells grown under N_(2) and under NH_(4)~(+)(30 mmol/L) respectively were used in this study. The specific activity of Af2 was 1540 nmol C_(2)H_(4)formed mg~(-1) protein min~(-1). and no activity of Af*2 was observed. The circular dichoism(CD)and magnetic CD(MCD)were measured in both reduced and oxidized states. Af2 and Af*2 differed from each other in their CD spectra, particularly in the oxidized states. After oxidization, the 210 nm peak of the CD spectra from Af2 was shifted to the far-UV region, while the spectra of Af*2 was almost unchanged. The MCD spectra of the reduced states of Af2 and Af*2 were quite different, but these of the oxidized states were the same, suggesting that their molecular structure and the environmental conditions around the 4Fe-4S cluster might be different.

Key words: Alcaligenes faecalis;Iron protein;Nitrogenase;CD spectra;Thermodynamic parameter

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Citing This Article：

Hai Weili, Song Wei, You Chongbiao, Li Zhong, Wang Wenqing. The CD spectra and thermodynamic properties of the iron protein of nitrogenase from N_(2)-and NH~(+)_(4)-grown Alcaligenes faecalis. Acta Physiol Sin 1994; 46 (1): (in Chinese with English abstract).