期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1972
卷号：69
期号：11
页码：3142-3145
DOI：10.1073/pnas.69.11.3142
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The electron paramagnetic resonance of nitrogenase components, separately and together with the other reactants in the nitrogenase system (namely, reductant and Mg{middle dot}ATP), have been examined at low temperatures (<20{degrees}K). The MoFe protein, component I or molybdoferredoxin, in the oxidized (but not oxygen-inactivated) state yields signals with g-values of 4.3, 3.7, and 2.01, and when reduced has no observable electron paramagnetic resonance. The Fe protein, component II, or azoferredoxin, yields a signal with g-values of 2.05, 1.94, and 1.89 in the reduced state that is converted by Mg{middle dot}ATP into an axial signal with g-values near 2.05 and 1.94, and a second split signal near g = 4.3. The Fe protein has no definite electron paramagnetic resonance in the oxidized (not oxygen-denatured) state under these conditions. The Mg{middle dot}ATP complex of reduced Fe protein reduces the MoFe protein, whereas dithionite alone does not reduce the MoFe protein. Reoxidation of the system by substrate leads to disappearance of the Fe protein signal and the reappearance of the MoFe protein signal. Thus Mg{middle dot}ATP, which is hydrolyzed during substrate reduction, converts the Fe protein to a reductant capable of transferring electrons to MoFe protein, after which substrate reduction occurs.
关键词：iron-sulfur proteins ; ferredoxins ; electron transfer ; nitrogen fixation ; Mg·ATP
