Structural and Dynamic Features of the MutT Protein in the Recognition of Nucleotides with the Mutagenic 8-Oxoguanine Base |
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Authors: | Teruya Nakamura Sachiko Meshitsuka Seiju Kitagawa Nanase Abe Junichi Yamada Tetsuya Ishino Hiroaki Nakano Teruhisa Tsuzuki Takefumi Doi Yuji Kobayashi Satoshi Fujii Mutsuo Sekiguchi Yuriko Yamagata |
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Affiliation: | From the ‡Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, ;the §Graduate School of Pharmaceutical Sciences, Osaka University, Suita 565-0871, ;the ¶Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, ;the ‖School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, and ;the **Fukuoka Dental College, Fukuoka 814-0193, Japan |
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Abstract: | Escherichia coli MutT hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, an event that can prevent the misincorporation of 8-oxoguanine opposite adenine in DNA. Of the several enzymes that recognize 8-oxoguanine, MutT exhibits high substrate specificity for 8-oxoguanine nucleotides; however, the structural basis for this specificity is unknown. The crystal structures of MutT in the apo and holo forms and in the binary and ternary forms complexed with the product 8-oxo-dGMP and 8-oxo-dGMP plus Mn2+, respectively, were determined. MutT strictly recognizes the overall conformation of 8-oxo-dGMP through a number of hydrogen bonds. This recognition mode revealed that 8-oxoguanine nucleotides are discriminated from guanine nucleotides by not only the hydrogen bond between the N7-H and Oδ (N119) atoms but also by the syn glycosidic conformation that 8-oxoguanine nucleotides prefer. Nevertheless, these discrimination factors cannot by themselves explain the roughly 34,000-fold difference between the affinity of MutT for 8-oxo-dGMP and dGMP. When the binary complex of MutT with 8-oxo-dGMP is compared with the ligand-free form, ordering and considerable movement of the flexible loops surrounding 8-oxo-dGMP in the binary complex are observed. These results indicate that MutT specifically recognizes 8-oxoguanine nucleotides by the ligand-induced conformational change. |
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