title: Molecular Basis of Hydroperoxide Specificity in Peroxiredoxins: The Case of AhpE from Mycobacterium tuberculosis.
abstract: Peroxiredoxins (Prxs) constitute a ubiquitous family of Cys-dependent peroxidases that play essential roles in reducing hydrogen peroxide, peroxynitrite, and organic hydroperoxides in almost all organisms. Members of the Prx subfamilies show differential oxidizing substrate specificities that await explanations at a molecular level. Among them, alkyl hydroperoxide reductases E (AhpE) is a novel subfamily comprising Mycobacterium tuberculosis AhpE and AhpE-like proteins expressed in some bacteria and archaea. We previously reported that MtAhpE reacts ∼10(4) times faster with an arachidonic acid derived hydroperoxide than with hydrogen peroxide, and suggested that this surprisingly high reactivity was related to the presence of a hydrophobic groove at the dimer interface evidenced in the crystallography structure of the enzyme. In this contribution we experimentally confirmed the existence of an exposed hydrophobic patch in MtAhpE. We found that fatty acid hydroperoxide reduction by the enzyme showed positive activation entropy that importantly contributed to catalysis. Computational dynamics indicated that interactions of fatty acid-derived hydroperoxides with the enzyme properly accommodated them inside the active site and modifies enzyme's dynamics. The computed reaction free energy profile obtained via QM/MM simulations is consistent with a greater reactivity in comparison with hydrogen peroxide. This study represents new insights on the understanding of the molecular basis that determines oxidizing substrate selectivity in the peroxiredoxin family, which has not been investigated at an atomic level so far.
authors.forename: Ari
authors.initials: A
authors.lastname: Zeida
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo 11800, Uruguay.
authors.forename: Aníbal M
authors.initials: AM
authors.lastname: Reyes
authors.forename: Pablo
authors.initials: P
authors.lastname: Lichtig
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo 11800, Uruguay.
authors.forename: Martín
authors.initials: M
authors.lastname: Hugo
authors.forename: Diego S
authors.initials: DS
authors.lastname: Vazquez
authors.forename: Javier
authors.initials: J
authors.lastname: Santos
authors.forename: F Luis
authors.initials: FL
authors.lastname: González Flecha
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo 11800, Uruguay.
authors.forename: Rafael
authors.initials: R
authors.lastname: Radi
authors.forename: Dario A
authors.initials: DA
authors.lastname: Estrin
authors.affiliation: Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo 11800, Uruguay.
authors.forename: Madia
authors.initials: M
authors.lastname: Trujillo
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D054464:Peroxiredoxins / Q000737:chemistry*; D055503:Protein Multimerization; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D054464:Peroxiredoxins