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).

ABSTRACT: Both ATP and a bivalent nucleotide-bound metal activator, normally Mg2+, 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 lambda=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 3.6 MHz and a relatively broad resonance at 8 MHz originating from a superhyperfine coupling to a 31P nuclear spin

SUBMITTER: Petersen J 

PROVIDER: S-EPMC1276953 | biostudies-literature | 2005 Nov

REPOSITORIES: biostudies-literature