A methyldiazene (HN=N-CH3)-derived species bound to the nitrogenase active-site FeMo cofactor: Implications for mechanism.

ABSTRACT: Methyldiazene (HN=N-CH3) isotopomers labeled with 15N at the terminal or internal nitrogens or with 13C or 2H were used as substrates for the nitrogenase alpha-195Gln-substituted MoFe protein. Freeze quenching under turnover traps an S = (1/2) state that has been characterized by EPR and 1H-, 15N-, and 13C-electron nuclear double resonance spectroscopies. These studies disclosed the following: (i) a methyldiazene-derived species is bound to the active-site FeMo cofactor; (ii) this species binds through an [-NHx] fragment whose N derives from the methyldiazene terminal N; and (iii) the internal N from methyldiazene probably does not bind to FeMo cofactor. These results constrain possible mechanisms for reduction of methyldiazene. In the Chatt-Schrock mechanism for N2 reduction, H atoms sequ

SUBMITTER: Barney BM 

PROVIDER: S-EPMC1693872 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature