Analysis of active sites for N_2 and H~+ reduction on FeMo-cofactor of nitrogenase

摘要

Dinitrogen (N_2) and proton (H~+), which act as physiological substrates of nitrogenase, are reduced on FeMo-co of the MoFe protein. However, researchers have different opinions about their exact reduction sites. Nitrogenases were purified from the wild type (WT) and five mutants of Azotobacter vinelandii (Av), including Qα191K, Hα195Q, nifV~-, Qα191KifV~- and Ha195QifV~-; and the activities of these enzymes for N_2 and H~+ reduction were analyzed. Our results suggest that the Fe2 and Fe6, atoms closed to the central sulfur atom (S2B) within FeMo-co, are sites for N_2 binding and reduction and the Mo atom of FeMo-co is the site for H~+ reduction. Combining these data with further bioinformatical analysis, we propose that two parallel electron channels may exist between the [8Fe7S] cluster and FeMo-co.