Hernandez Jose A, Curatti Leonardo, Aznar Constantino P, Perova Zinaida, Britt R David, Rubio Luis M
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
Proc Natl Acad Sci U S A. 2008 Aug 19;105(33):11679-84. doi: 10.1073/pnas.0803576105. Epub 2008 Aug 12.
The molybdenum nitrogenase, present in a diverse group of bacteria and archea, is the major contributor to biological nitrogen fixation. The nitrogenase active site contains an iron-molybdenum cofactor (FeMo-co) composed of 7Fe, 9S, 1Mo, one unidentified light atom, and homocitrate. The nifQ gene was known to be involved in the incorporation of molybdenum into nitrogenase. Here we show direct biochemical evidence for the role of NifQ in FeMo-co biosynthesis. As-isolated NifQ was found to carry a molybdenum-iron-sulfur cluster that serves as a specific molybdenum donor for FeMo-co biosynthesis. Purified NifQ supported in vitro FeMo-co synthesis in the absence of an additional molybdenum source. The mobilization of molybdenum from NifQ required the simultaneous participation of NifH and NifEN in the in vitro FeMo-co synthesis assay, suggesting that NifQ would be the physiological molybdenum donor to a hypothetical NifEN/NifH complex.
钼固氮酶存在于多种细菌和古菌中，是生物固氮的主要贡献者。固氮酶活性位点包含一个由7个铁原子、9个硫原子、1个钼原子、一个未鉴定的轻原子和高柠檬酸组成的铁钼辅因子（FeMo-co）。已知nifQ基因参与钼掺入固氮酶的过程。在此，我们展示了NifQ在FeMo-co生物合成中作用的直接生化证据。发现分离得到的NifQ携带一个钼铁硫簇，该簇作为FeMo-co生物合成的特定钼供体。在没有额外钼源的情况下，纯化的NifQ支持体外FeMo-co合成。在体外FeMo-co合成测定中，钼从NifQ的转移需要NifH和NifEN同时参与，这表明NifQ可能是一个假设的NifEN/NifH复合物的生理钼供体。
