Conformationally Gated Electron Transfer in Nitrogenase. Isolation, Purification, and Characterization of Nitrogenase From Gluconacetobacter diazotrophicus
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Nitrogenase is a complex, bacterial enzyme that catalyzes the ATP-dependent reduction of dinitrogen (N2) to ammonia (NH3). In its most prevalent form, it consists of two proteins, the catalytic molybdenum-iron protein (MoFeP) and its specific reductase, the iron protein (FeP). A defining feature of nitrogenase is that electron and proton transfer processes linked to substrate reduction are synchronized by conformational changes driven by ATP-dependent FeP-MoFeP interactions. Yet, despite extensice crystallographic, spectroscopic, and biochemical information on nitrogenase, the structural basis of the ATP-dependent synchronization mechanism is not understood in detail. In this chapter, we summarize some of our efforts toward obtaining such an understanding.
Experimental investigations of the structure-function relationships in nitrogenase are challenged by the fact that it cannot be readily expressed herterlogously in non-diazotrophic bacteria, and the purification protocols for nitrogenase are only known for a small number of diazotrophic organisms. Here, we present methods for purifying and characterizing nitrogenase from a new model organism, Gluconacetobacter diazotrophicus. We also describe procedures for observing redox-dependent conformational changes in G. diazotrophicus nitrogenase by X-ray crystallography and electron paramagnetic resonance spectroscopy, which have provided new insights into the redox-dependent conformational gating processes in nitrogenase.
Amino Acids, Peptides, and Proteins | Environmental Chemistry | Enzymes and Coenzymes | Laboratory and Basic Science Research | Organic Chemistry | Other Chemistry | Physical Chemistry | Research Methods in Life Sciences
Owens, C. P., & Tezcan, F. A. (2018). Conformationally gated electron transfer in nitrogenase. Isolation, purification, and characterization of nitrogenase from Gluconacetobacter diazotrophicus. Methods in Enzymology, 599, 355-386. doi:10.1016/bs.mie.2017.09.007