Fungal laccases, belonging to the multicopper oxidases, can catalyze the oxidation of a large number of aromatic (especially phenolic), inorganic and xenobiotic compounds. In multicopper oxidases, the T1 Cu site accepts electrons from the substrate and transfers them to a T2/T3 trinuclear Cu cluster, which binds and activates O2 for reduction to H2O. The first X-ray structure available for a laccase, from Coprinus Cinereus, reveals a molecular architecture consisting of three b-barrel cupredoxin-like domains.1 In order to assess the structural features helping the phenolic substrates recognition, we have performed a comparative structural study on three fungal laccases: the one from Coprinus Cinereus, and two (POXC and POXA1b) from Pleurotus Ostreatus. Homology models are employed for POXC and POXA1b. First, a channel providing access to the T1 copper site, about 7 Å deep, is located at the interface between the structural domains 2 and 3. The T1-copper coordinating His457, analogous to the coordinating histidines involved in the electron transfer to other copper-proteins, is solvent exposed at the channel bottom. Docking calculations are then performed in such a cleft for two phenolic compounds: 2,6-di-methoxyphenol (DMP) and 2,6-di-t-butylphenol (DTBP), respectively a good and a bad substrate2 for laccases. The hydroxyl reducing group of DMP is shown to be at catalytic distance from His457. A possible role in assisting the catalytic oxidation is also suggested for Asp205, which forms an H-bond with the phenolic hydroxyl group and is conserved among fungal laccases. On the contrary, DTBP is shown not to match the cleft. A structure based sequence alignment between fungal laccases and the homologous ascorbate oxidase (AO)3 is also presented, which allows to outline a significant correspondence between their predicted substrate pockets. References 1. Ducros V. et al. (1998) Nature Struct. Biol. 5, 310. 2. Xu F. (1996) Biochemistry 35, 323. 3. Messerschmidt A. et al. (1992) J. Mol. Biol. 224, 179.

A binding pocket for phenolic substrates in laccases

OLIVA, Romina;
2002-01-01

Abstract

Fungal laccases, belonging to the multicopper oxidases, can catalyze the oxidation of a large number of aromatic (especially phenolic), inorganic and xenobiotic compounds. In multicopper oxidases, the T1 Cu site accepts electrons from the substrate and transfers them to a T2/T3 trinuclear Cu cluster, which binds and activates O2 for reduction to H2O. The first X-ray structure available for a laccase, from Coprinus Cinereus, reveals a molecular architecture consisting of three b-barrel cupredoxin-like domains.1 In order to assess the structural features helping the phenolic substrates recognition, we have performed a comparative structural study on three fungal laccases: the one from Coprinus Cinereus, and two (POXC and POXA1b) from Pleurotus Ostreatus. Homology models are employed for POXC and POXA1b. First, a channel providing access to the T1 copper site, about 7 Å deep, is located at the interface between the structural domains 2 and 3. The T1-copper coordinating His457, analogous to the coordinating histidines involved in the electron transfer to other copper-proteins, is solvent exposed at the channel bottom. Docking calculations are then performed in such a cleft for two phenolic compounds: 2,6-di-methoxyphenol (DMP) and 2,6-di-t-butylphenol (DTBP), respectively a good and a bad substrate2 for laccases. The hydroxyl reducing group of DMP is shown to be at catalytic distance from His457. A possible role in assisting the catalytic oxidation is also suggested for Asp205, which forms an H-bond with the phenolic hydroxyl group and is conserved among fungal laccases. On the contrary, DTBP is shown not to match the cleft. A structure based sequence alignment between fungal laccases and the homologous ascorbate oxidase (AO)3 is also presented, which allows to outline a significant correspondence between their predicted substrate pockets. References 1. Ducros V. et al. (1998) Nature Struct. Biol. 5, 310. 2. Xu F. (1996) Biochemistry 35, 323. 3. Messerschmidt A. et al. (1992) J. Mol. Biol. 224, 179.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11367/21414
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