Role of calcium in metalloenzymes: effects of calcium removal on the axial ligation geometry and magnetic properties of the catalytic diheme center in MauG.

ABSTRACT: MauG is a diheme enzyme possessing a five-coordinate high-spin heme with an axial His ligand and a six-coordinate low-spin heme with His-Tyr axial ligation. A Ca(2+) ion is linked to the two hemes via hydrogen bond networks, and the enzyme activity depends on its presence. Removal of Ca(2+) altered the electron paramagnetic resonance (EPR) signals of each ferric heme such that the intensity of the high-spin heme was decreased and the low-spin heme was significantly broadened. Addition of Ca(2+) back to the sample restored the original EPR signals and enzyme activity. The molecular basis for this Ca(2+)-dependent behavior was studied by magnetic resonance and Mössbauer spectroscopy. The results show that in the Ca(2+)-depleted MauG the high-spin heme was converted to a low-spin heme and the

SUBMITTER: Chen Y 

PROVIDER: S-EPMC3294375 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature