Structural and dynamic features of the MutT protein in the recognition of nucleotides with the mutagenic 8-oxoguanine base.
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 Mn(2+), 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 Odelta (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.
Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan.
Teruya
T
Nakamura
Sachiko
S
Meshitsuka
Seiju
S
Kitagawa
Nanase
N
Abe
Junichi
J
Yamada
Tetsuya
T
Ishino
Hiroaki
H
Nakano
Teruhisa
T
Tsuzuki
Takefumi
T
Doi
Yuji
Y
Kobayashi
Satoshi
S
Fujii
Mutsuo
M
Sekiguchi
Yuriko
Y
Yamagata
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003848:Deoxyguanine Nucleotides / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D008670:Metals / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000235:genetics*; D009711:Nucleotides / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011755:Pyrophosphatases / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D001059:Apoproteins; D003848:Deoxyguanine Nucleotides; D029968:Escherichia coli Proteins; D008670:Metals; D009711:Nucleotides; C024829:8-hydroxyguanine; D006147:Guanine; D011755:Pyrophosphatases; C052211:mutT protein, E coli