Pulsed EPR studies of the exchangeable proton at the molybdenum center of dimethyl sulfoxide reductase.
Electron spin echo envelope modulation (ESEEM) spectroscopy has been used to determine the hyperfine ( hfi) and quadrupole ( nqi) interactions of the exchangeable deuteron (proton) at the Mo(V) site of DMSO reductase. The data obtained have been translated into structure-related parameters. It was found that isotropic hfi constant of the proton is not unique, but is distributed within a range of 26-36 MHz. From this hfi distribution, a 30 degrees -wide distribution of the OH bond orientations due to a rotation around the Mo-O bond was estimated. The angle between the axes of the nqi and anisotropic hfi tensors was found to be anomalously small in comparison with that expected from the Mo-O-D bond geometry. This peculiarity was attributed to the effect of spin density on the hydroxyl oxygen atom. The orientation of the Mo-OH fragment with respect to the g-frame was determined from the experimental orientations of the nqi and hfi tensor axes and a theoretical evaluation of the anisotropic hfi axis direction.
Raitsimring
Arnold M
AM
Department of Chemistry, University of Arizona, Tucson, AZ 85721-0041, USA.
Astashkin
Andrei V
AV
Feng
Changjian
C
Enemark
John H
JH
Nelson
Kimberly Johnson
KJ
Rajagopalan
K V
KV
D003903:Deuterium / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D007506:Iron-Sulfur Proteins; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry*; D010088:Oxidoreductases / Q000737:chemistry*; D011522:Protons; D011994:Recombinant Proteins / Q000737:chemistry; D013329:Structure-Activity Relationship
D007506:Iron-Sulfur Proteins; D011522:Protons; D011994:Recombinant Proteins; D008982:Molybdenum; D003903:Deuterium; D010088:Oxidoreductases; C045664:dimethyl sulfoxide reductase