2 research outputs found
La Recerca en el camp de l'etnologia marÃtima i pesquera: taula rodona
Taula rodona emmarcada dins la II Jornada d'Etnologia a la Costa Brava: la recerca en el camp de l'etnologia maÃtima i pesquer
Eukaryotic Catalase-Peroxidase: The Role of the Trp-Tyr-Met Adduct in Protein Stability, Substrate Accessibility, and Catalysis of Hydrogen Peroxide Dismutation
Recently, it was demonstrated that
bifunctional catalase-peroxidases
(KatGs) are found not only in archaea and bacteria but also in lower
eukaryotes. Structural studies and preliminary biochemical data of
the secreted KatG from the rice pathogen <i>Magnaporthe grisea</i> (<i>Mag</i>KatG2) suggested both similar and novel features
when compared to those of the prokaryotic counterparts studied so
far. In this work, we demonstrate the role of the autocatalytically
formed redox-active Trp140-Tyr273-Met299 adduct of <i>Mag</i>KatG2 in (i) the maintenance of the active site architecture, (ii)
the catalysis of hydrogen peroxide dismutation, and (iii) the protein
stability by comparing wild-type <i>Mag</i>KatG2 with the
single mutants Trp140Phe, Tyr273Phe, and Met299Ala. The impact of
disruption of the covalent bonds between the adduct residues on the
spectral signatures and heme cavity architecture was small. By contrast,
loss of its integrity converts bifunctional <i>Mag</i>KatG2
to a monofunctional peroxidase of significantly reduced thermal stability.
It increases the accessibility of ligands due to the increased flexibility
of the KatG-typical large loop 1 (LL1), which contributes to the substrate
access channel and anchors at the adduct Tyr. We discuss these data
with respect to those known from prokaryotic KatGs and in addition
present a high-resolution structure of an oxoiron compound of <i>Mag</i>KatG2