Serial femtosecond zero dose crystallography captures a water‐free distal heme site in a dye‐decolorising peroxidase to reveal a catalytic role for an arginine in FeIV=O Formation

Lučić, Marina, Svistunenko, Dimitri A., Wilson, Michael T., Chaplin, Amanda K., Davy, Bradley, Ebrahim, Ali, Axford, Danny, Tosha, Takehiko, Sugimoto, Hiroshi, Owada, Shigeki, Dworkowski, Florian S. N, Tews, Ivo, Owen, Robin L., Hough, Michael A. and Worrall, Jonathan A. R. (2020) Serial femtosecond zero dose crystallography captures a water‐free distal heme site in a dye‐decolorising peroxidase to reveal a catalytic role for an arginine in FeIV=O Formation. Angewandte Chemie International Edition, 59 (48), 21656–21662. (doi:10.1002/anie.202008622).

Abstract

Obtaining structures of intact redox states of metal centers derived from zero dose X‐ray crystallography can advance our mechanistic understanding of metalloenzymes. In dye‐decolorising heme peroxidases (DyPs), controversy exists regarding the mechanistic role of the distal heme residues aspartate and arginine in the heterolysis of peroxide to form the catalytic intermediate compound I (FeIV=O and a porphyrin cation radical). Using serial femtosecond X‐ray crystallography (SFX), we have determined the pristine structures of the FeIII and FeIV=O redox states of a B‐type DyP. These structures reveal a water‐free distal heme site that, together with the presence of an asparagine, imply the use of the distal arginine as a catalytic base. A combination of mutagenesis and kinetic studies corroborate such a role. Our SFX approach thus provides unique insight into how the distal heme site of DyPs can be tuned to select aspartate or arginine for the rate enhancement of peroxide heterolysis.

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Contributors

Author: Ivo Tews

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