title: N coordination of FeMo cofactor requires His-195 of the MoFe protein alpha subunit and is essential for biological nitrogen fixation.
abstract: Electron spin echo envelope modulation (ESEEM) spectroscopy, a pulsed electron spin resonance technique, was used to analyze the N coordination of the iron-molybdenum (FeMo) cofactor contained within the nitrogenase MoFe protein. Comparison of spectra obtained from whole cells and purified MoFe protein established that the N coordination of the FeMo cofactor provided by the MoFe-protein polypeptide matrix can be unambiguously recognized in whole cells. ESEEM spectra of altered MoFe proteins, which were produced in certain mutant strains of Azotobacter vinelandii, showed that the N coordination to FeMo cofactor requires His-195 of the MoFe protein alpha subunit. Moreover, this requirement for His-195 was shown to be essential for biological nitrogen fixation.
authors.affiliation: Exxon Research and Engineering Co., Annandale, NJ 08801, USA.
authors.forename: H
authors.initials: H
authors.lastname: Thomann
authors.forename: M
authors.initials: M
authors.lastname: Bernardo
authors.forename: W E
authors.initials: WE
authors.lastname: Newton
authors.forename: D R
authors.initials: DR
authors.lastname: Dean