AI Article Synopsis
- The architecture of hemoproteins influences how heme coordinates, with a specific focus on the acidic residue Glu226 in ascorbate peroxidase from Leishmania major.
- Substituting Glu226 with Ala changes the heme's coordination from a 5 coordinate high spin (5cHS) form to a 6 coordinate low spin (6cLS) form at neutral pH, with hydroxo as the sixth ligand.
- At lower pH, the mutant Glu226Ala forms a new 6cHS species, but lacks key reactivity traits, indicating that Glu226 is crucial for maintaining the active site structure and function.
Article Abstract
Architecture of hemoprotein is solely responsible for different nature of heme coordination. Here we report that substitution of the acidic surface residue Glu226 to Ala in ascorbate peroxidase from Leishmania major alters the 5 coordinate high spin (5cHS) to a 6 coordinate low spin (6cLS) form at pH 7.5. Using UV-visible spectrophotometry, we show that the sixth ligand of heme in Glu226Ala at pH 7.5 is hydroxo. When the pH is decreased to 5.5, a new species of Glu226Ala appeared that had a spectrum characteristic of a 6cHS derivative. Stopped flow spectrophotometric techniques revealed that characteristics of Compound I was not seen in the Glu226Ala in presence of H(2)O(2). Similarly guaiacol, ascorbate and ferrocytochrome c oxidation rate was 10(3) orders less for the Glu226Ala mutants compared to the wild type. These data suggested that surface acidic residue Glu226 might play role in proper maintenance of active site conformation.
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| http://dx.doi.org/10.1016/j.abb.2010.01.002 | DOI Listing |
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