Mn2+-adenosine nucleotide complexes in the presence of the nitrogenase iron-protein: Detection of conformational rearrangements directly at the nucleotide binding site by EPR and 2D-ESEEM (two-dimensional electron spin-echo envelope modulation spectroscopy)

Jan Petersen, Christof Gessner, Karl Fisher, Claire J. Mitchell, David J. Lowe, Wolfgang Lubitz

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Both ATP and a bivalent nucleotide-bound metal activator, normally Mg 2+, are required for nitrogenase activity. EPR and ESEEM (electron spin-echo envelope modulation) measurements have been carried out on adenosine nucleotides in which the Mg2+ ion that is usually bound is replaced by Mn2+ in the presence of Kp2 (nitrogenase Fe-protein from Klebsiella pneumoniae). The Mn2+ zero-field splitting parameters have been determined from the EPR-spectrum to be |D| = 0.0125 cm-1 with a rhombicity λ = E|D = 0.31 by direct diagonalization of the complete spin Hamiltonian. ESEEM spectra of the Fe-protein with MnADP and MnATP both show an ESEEM line pair with one signal component at about 3.6MHz and a relatively broad resonance at 8 MHz originating from a superhyperfine coupling to a 31P nuclear spin from one or more directly co-ordinated phospho group(s) of the nucleotide. A pronounced resonance overlapping the low-frequency component of the 31P-signal at about 3.5 MHz is attributed to an interaction of Mn2+ with univalent 23Na nuclei. ESEEM lines at frequencies
    Original languageEnglish
    Pages (from-to)527-539
    Number of pages12
    JournalBiochemical Journal
    Volume391
    Issue number3
    DOIs
    Publication statusPublished - 1 Nov 2005

    Keywords

    • Electron paramagnetic resonance (EPR)
    • Electron spin-echo envelope modulation (ESEEM)
    • Fe-protein
    • Hydrolysis
    • Manganese
    • Nitrogenase

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