title: Comparative unfolding studies of psychrophilic and mesophilic uracil DNA glycosylase: MD simulations show reduced thermal stability of the cold-adapted enzyme.
abstract: Uracil DNA glycosylase (UDG) is a DNA repair enzyme involved in the base excision repair (BER) pathway, removing misincorporated uracil from the DNA strand. The native and mutant forms of Atlantic cod and human UDG have previously been characterized in terms of kinetic and thermodynamic properties as well as the determination of several crystal structures. This data shows that the cold-adapted enzyme is more catalytically efficient but at the same time less resistant to heat compared to its warm-active counterpart. In this study, the structure-function relationship is further explored by means of comparative molecular dynamics (MD) simulations at three different temperatures (375, 400 and 425K) to gain a deeper insight into the structural features responsible for the reduced thermostability of the cold-active enzyme. The simulations show that there are distinct structural differences in the unfolding pathway between the two homologues, particularly evident in the N- and C-terminals. Distortion of the mesophilic enzyme is initiated simultaneously in the N- and C-terminal, while the C-terminal part plays a key role for the stability of the psychrophilic enzyme. The simulations also show that at certain temperatures the cold-adapted enzyme unfolds faster than the warm-active homologues in accordance with the lower thermal stability found experimentally.
authors.affiliation: The Norwegian Structural Biology Centre, Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway.
authors.forename: Magne
authors.initials: M
authors.lastname: Olufsen
authors.forename: Bjørn Olav
authors.initials: BO
authors.lastname: Brandsdal
authors.forename: Arne Oskar
authors.initials: AO
authors.lastname: Smalås
mesh_terms: D000064:Acclimatization; D000818:Animals; D003081:Cold Climate; D003198:Computer Simulation; D004795:Enzyme Stability; D048389:Gadus morhua; D006801:Humans; D006860:Hydrogen Bonding; D066298:In Vitro Techniques; D008958:Models, Molecular; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013045:Species Specificity; D013816:Thermodynamics; D051981:Uracil-DNA Glycosidase / Q000737:chemistry*
chemical_list: D051981:Uracil-DNA Glycosidase