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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 Fe IV =O Formation
Author(s) -
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.,
Worrall Jonathan A. R.
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202008622
Subject(s) - heterolysis , chemistry , porphyrin , heme , peroxidase , peroxide , redox , catalysis , photochemistry , catalytic cycle , asparagine , arginine , stereochemistry , crystallography , inorganic chemistry , amino acid , enzyme , biochemistry , organic chemistry
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 (Fe IV =O and a porphyrin cation radical). Using serial femtosecond X‐ray crystallography (SFX), we have determined the pristine structures of the Fe III and Fe IV =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.