Determination of the distance between the Mo(V) and Fe(III) heme centers of wild type human sulfite oxidase by pulsed EPR spectroscopy.

ABSTRACT: Intramolecular electron transfer (IET) between the molybdenum and heme centers of vertebrate sulfite oxidase (SO) is proposed to be a key step in the catalytic cycle of the enzyme. However, the X-ray crystallographic distance between these centers, R(MoFe) = 32.3 Å, appears to be too long for the rapid IET rates observed in liquid solution. The Mo and heme domains are linked by a flexible tether, and it has been proposed that dynamic interdomain motion brings the two metal centers closer together and thereby facilitates rapid IET. To date, there have been no direct distance measurements for SO in solution that would support or contradict this model. In this work, pulsed electron-electron double resonance (ELDOR) and relaxation induced dipolar modulation enhancement (RIDME) techniques were

SUBMITTER: Astashkin AV 

PROVIDER: S-EPMC3288158 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature