title: Structural Basis of Substrate Specificity in Geobacter metallireducens SMUG1.
abstract: Base deamination is a common type of DNA damage that occurs in all organisms. DNA repair mechanisms are critical to maintain genome integrity, in which the base excision repair pathway plays an essential role. In the BER pathway, the uracil DNA glycosylase superfamily is responsible for removing the deaminated bases from DNA and generates apurinic/apyrimidinic (AP) sites. Geobacter metallireducens SMUG1 (GmeSMUG1) is an interesting family 3 enzyme in the UDG superfamily, with dual substrate specificities for DNA with uracil or xanthine. In contrast, the mutant G63P of GmeSMUG1 has exclusive activity for uracil, while N58D is inactive for both substrates, as we have reported previously. However, the structural bases for these substrate specificities are not well understood. In this study, we solved a series of crystal structures of WT and mutants of GmeSMUG1 at relatively high resolutions. These structures provide insight on the molecular mechanism of xanthine recognition for GmeSMUG1 and indicate that H210 plays a key role in xanthine recognition, which is in good agreement with the results of our EMSA and activity assays. More importantly, our mutant structures allow us to build models to rationalize our previous experimental observations of altered substrate activities of these mutants.
authors.affiliation: State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University , 135 W. Xingang Rd., Guangzhou, Guangdong 510275, People's Republic of China.|Center for Cellular & Structural Biology, The Sun Yat-Sen University , 132 E. Circle Rd., University City, Guangzhou, Guangdong 510006, People's Republic of China.
authors.forename: Zhemin
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University , 135 W. Xingang Rd., Guangzhou, Guangdong 510275, People's Republic of China.|Center for Cellular & Structural Biology, The Sun Yat-Sen University , 132 E. Circle Rd., University City, Guangzhou, Guangdong 510006, People's Republic of China.
authors.forename: Jiemin
authors.initials: J
authors.lastname: Shen
authors.affiliation: Department of Genetics and Biochemistry, Clemson University , South Carolina Experiment Station, 190 Collings Street, Clemson, South Carolina 29634, United States.
authors.forename: Ye
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Genetics and Biochemistry, Clemson University , South Carolina Experiment Station, 190 Collings Street, Clemson, South Carolina 29634, United States.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Genetics and Biochemistry, Clemson University , South Carolina Experiment Station, 190 Collings Street, Clemson, South Carolina 29634, United States.
authors.forename: Weiguo
authors.initials: W
authors.lastname: Cao
authors.affiliation: State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University , 135 W. Xingang Rd., Guangzhou, Guangdong 510275, People's Republic of China.|Center for Cellular & Structural Biology, The Sun Yat-Sen University , 132 E. Circle Rd., University City, Guangzhou, Guangdong 510006, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xie
mesh_terms: D018360:Crystallography, X-Ray; D045302:Geobacter / Q000201:enzymology*; D015394:Molecular Structure; D013379:Substrate Specificity; D051981:Uracil-DNA Glycosidase / Q000737:chemistry*; D019820:Xanthine / Q000737:chemistry
chemical_list: D019820:Xanthine; D051981:Uracil-DNA Glycosidase