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

Dinitrogen (N2) 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-,Qα191K/nifV- and Hα195Q/nifV-; and the activities of these en-zymes for N2 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 N2 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.

Dinitrogen （N2） 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 Qo191K, Ho195Q, nffV-, Qcr191KInifV- and Hcr195Q/nffV-; and the activities of these enzymes for N2 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 N2 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.