201805Nakamura

研究発表を行った学会；
2017 West Coast Protein Crystallography Workshop
2017年3月19日〜22日（Asiloma, US）
タイトル；Role of protonation at Asp residues in the broad substrate specificity of human oxidative nucleotide hydrolase.
発表者；中村　照也　氏
（熊本大学　大学院先導機構）
要旨；
Reactive oxygen species, which are generated in normal cellular metabolism, oxidize DNA, RNA and their precursor nucleotides. Oxdative nucleoside triphosphates such as 8-oxo-dGTP induce transversion mutations because of their misincorporation into a newly synthesized strand during DNA replication. In Escherichia coli, MutT hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP with extremely high substrate specificity (14,000-fold higher affinity than that for dGTP), and prevents the transversion mutations. The structural study has revealed that MutT recognizes characteristic features of 8-oxoG nucleotide, which are O8 and N7-H atoms of 8-oxoG base and its overall syn glycosidic conformation, by a number of hydrogen bonds through the large ligand-induced conformational change of MutT. In contrast to MutT, its human homolog, human MTH1 (hMTH1) hydrolyzes 8-oxo-dGTP and 2-oxo-dATP to the corresponding monophosphates with its broad substrate specificity. Recently, our structural and kinetic studies of hMTH1 have shown that hMTH1 recognizes 8-oxo-dGTP and 2-oxo-dATP by changing the protonation state at the Asp residues in the substrate-binding site for each substrate. In order to experimentally verify the protonation state at the Asp residues, we have examined the bond-lengths of the Asp residues (C-Oδ1 and C-Oδ2) with the high-resolution crystal structures of hMTH1 by unrestrained refinement using SHELXL. The protonation state examined by the bond-length analysis was consistent with the results of our structural and kinetic studies. Here we describe the mechanism of the broad substrate specificity of hMTH1 via protonation of the Asp residues.