title: Laccase Redox Potentials: pH Dependence and Mutants, a QM/MM Study.
abstract: We have studied the T. versicolor laccase T1 site redox potential (RP) at the M06/6-311++G**/SDD(Cu) level of theory, employing QM/MM-optimized geometries (RI-BP86/def2-SVP/def2-TZVP(Cu):CHARMM) of the whole protein system with electronic embedding. The oxidation state of the trinuclear cluster was found to affect the T1 site RP by about 0.2-0.3 V, depending on the protein protonation state. The computed laccase RP can be drastically lowered upon introduction of a protonation state corresponding to a neutral environment, by up to -1.37 V, which is likely an overestimation of the effect in vivo. The gradual change of the protonation state by single points without optimization or equilibration results in a change that is even larger, namely up to about -2.6 V. Thus, the preferred protein conformation supports a high redox potential, compensating for the RP-lowering effect of surface charges. The predicted change in RP on going to the F463M mutant, ca. -0.1 V, is consistent with observations for a related laccase. Based on our results, we also propose and test a D206N mutant but find it to be locked in a conformation with slightly lower RP.
authors.affiliation: EastChem School of Chemistry, University of St Andrews , North Haugh, St Andrews, Fife KY16 9ST, U.K.
authors.forename: Jan P
authors.initials: JP
authors.lastname: Götze
authors.affiliation: EastChem School of Chemistry, University of St Andrews , North Haugh, St Andrews, Fife KY16 9ST, U.K.
authors.forename: Michael
authors.initials: M
authors.lastname: Bühl
mesh_terms: D006863:Hydrogen-Ion Concentration; D042845:Laccase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D011522:Protons; D011789:Quantum Theory; D014010:Tinea Versicolor / Q000201:enzymology
chemical_list: D011522:Protons; D042845:Laccase