Characterization of the defect in the Escherichia coli mutT1 mutator gene

Bhatnagar, S. K.; Bullions, L C; Lew, G; Bessman, Maurice J.

doi:10.1128/jb.172.5.2802-2803.1990

Cited by 30 publications

(34 citation statements)

References 15 publications

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“…The glycosidic conformation of 8-oxo-dGMP bound to MutT is syn. This fact is consistent with the first suggestion by Bessman et al that MutT may recognize the syn conformation, because the 8-substituted purine nucleotides were better substrates compared with the normal purine nucleotides (42). The sugar ring puckering and the sugar-phosphate backbone conformation of 8-oxo-dGMP are C2Ј-endo and gauche Ϫ -trans, respectively.…”

Section: Resultssupporting

confidence: 80%

Structural and Dynamic Features of the MutT Protein in the Recognition of Nucleotides with the Mutagenic 8-Oxoguanine Base

Nakamura

Meshitsuka

Kitagawa

et al. 2010

Journal of Biological Chemistry

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Escherichia coli MutT hydrolyzes 8-oxo-dGTP to 8-oxodGMP, 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-oxodGMP 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 O␦ (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-oxodGMP in the binary complex are observed. These results indicate that MutT specifically recognizes 8-oxoguanine nucleotides by the ligand-induced conformational change.Although spontaneous mutations are indispensable to the evolutionary process of living organisms, they can also be lethal to the organism. Among the various modified bases in DNA, RNA, and nucleotides, 8-oxoguanine (8-oxoG), 2 a damaged form of guanine (G) generated by reactive oxygen species, is known to have highly mutagenic potency because of its mispairing with adenine. Therefore, organisms have an error avoidance pathway for preventing mutations caused by 8-oxoG. The Escherichia coli MutT protein (129 amino acids, M r ϭ 14,900) hydrolyzes 8-oxo-dGTP and 8-oxo-GTP to their corresponding nucleoside monophosphates and inorganic pyrophosphate in the presence of Mg 2ϩ (1, 2). Because 8-oxodGTP and 8-oxo-GTP can be misincorporated opposite adenine by DNA and RNA polymerases, the hydrolysis of the damaged nucleotides by MutT can avoid replicational and transcriptional errors. In DNA, 8-oxoG paired with cytosine is excised by MutM, an 8-oxoG DNA glycosylase, whereas MutY, an adenine DNA glycosylase, removes adenine paired with 8-oxoG (3-6).The substrate specificities of enzymes that recognize 8-oxoG are quite varied. MutT exhibits high substrate specificity for 8-oxoG nucleotides; that is, the K m for 8-oxo-dGTP is 14,000-fold lower than that for dGTP (7). In contrast, human MutT homologue 1 (hMTH1) hydrolyzes not only 8-oxo-dGTP but also several oxidized purine nucleotides such as 2-oxo-dATP, 2-oxo-ATP, 8-oxo-dATP, and 8-oxo-ATP. In terms of the hydrolysis of 8-oxo-dGTP, the K m of hMTH1 for 8-oxo-dGTP is only 17-fold lower than that for dGTP (8, 9). The solution structure of hMTH1 as determined by NMR has revealed its overall architecture and possible substrate-binding region ...

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Section: Resultssupporting

confidence: 80%

Structural and Dynamic Features of the MutT Protein in the Recognition of Nucleotides with the Mutagenic 8-Oxoguanine Base

Nakamura

Meshitsuka

Kitagawa

et al. 2010

Journal of Biological Chemistry

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“…Ca 2ϩ sensing and the apparent ADP-ribose pyrophosphatase property of TRPM2 may, however, not be related. Studies with other Nudix motif-containing proteins revealed that Mn 2ϩ , Zn 2ϩ , and Ca 2ϩ are only 15-40% as effective as Mg 2ϩ in supporting enzymatic activity (16,17).…”

Section: Ca 2ϩ Dependence Of Trpm2mentioning

confidence: 99%

Critical Intracellular Ca2+ Dependence of Transient Receptor Potential Melastatin 2 (TRPM2) Cation Channel Activation

McHugh

Flemming

et al. 2003

Journal of Biological Chemistry

248

240

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TRPM2 is a member of the melastatin-related TRP (transient receptor potential) subfamily. It is expressed in brain and lymphocytes and forms a cation channel that is activated by intracellular ADP-ribose and associated with cell death. In this study we investigated the calcium dependence of human TRPM2 expressed under a tetracycline-dependent promoter in HEK-293 cells. TRPM2 expression was associated with enhanced hydrogen peroxide-evoked intracellular calcium signals. In whole-cell patch clamp recordings, switching from barium-to calcium-containing extracellular solution markedly activated TRPM2 as long as ADP-ribose was in the patch pipette and exogenous intracellular calcium buffering was minimal. We suggest this effect reveals a critical dependence of TRPM2 channel activity on intracellular calcium. In the absence of extracellular calcium we observed concentration-dependent activation of TRPM2 channels by calcium delivered from the patch pipette (EC 50 340 nM, slope 4.9); the maximum effect was at least as large as that evoked by extracellular calcium. Intracellular dialysis of cells with high concentrations of EGTA or 1,2-bis(o-Aminophenoxy)ethane-N,N,N,Ntetraacetic acid (BAPTA) strongly reduced the amplitude of the extracellular calcium response, and the residual response was abolished by a mixture of high and low affinity calcium buffers. TRPM2 channel currents in inside-out patches showed a strong requirement for Ca 2؉ at the intracellular face of the membrane. We suggest that calcium entering via TRPM2 proteins acts at an intracellular calcium sensor closely associated with the channel, providing essential positive feedback for channel activation.The non-voltage-gated TRP Ca 2ϩ channel encoded by the transient receptor potential (trp) 1 gene has a major role in the phospholipase C-dependent light response of the Drosophila photoreceptor (1). Since this discovery, many trp-related Ca 2ϩ channels have been discovered in mammals, beginning with TRPC1 (e.g. Ref.2), which is a subunit of some store-operated Ca 2ϩ channels (e.g. Ref.3). There are now known to be at least 20 trp-related mammalian genes, all apparently encoding cationic channels, many of which are Ca 2ϩ permeable. They would appear to be the molecular basis of the many non-voltage-gated cationic channels with diverse functions and expression profiles in mammalian systems. On the basis of amino acid sequence the mammalian TRPs are divided into three subgroups, TRPC (C, canonical), TRPV (V, vanilloid receptor), and TRPM (M, melastatin receptor) (4). Increasingly it is becoming apparent that the regulation of these proteins is complex, with gating factors as diverse as temperature, menthol, diacylglycerol, arachidonic acid, and osmotic stress (5, 6).TRPM2 (also called TRPC7 or LTRPC2) is a recently characterized member of the TRPM family (7-11). It forms a cationic channel activated by intracellular ADP-ribose, ␤-NAD ϩ , or arachidonic acid. The sensitivity of the channel to ␤-NAD ϩ is thought to couple TRPM2 to the redox state of the cell (10). T...

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“…9 This lesion is repaired by several enzymes, and it has been suggested that the higher population of the syn conformation on 8-oxoG is the structural feature recognized by the repair enzymes to distinguish 8-oxoG and dG. 10 Bulky substituents on purine nucleosides at the 8-position shift the equilibrium to the syn conformation. 11 On the basis of these data, 8-bromo-2'-deoxyguanosine (B) was successfully used to probe syn-anti conformational preferences on G-quartet structures.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Properties of Oligonucleotides Containing 8-Bromo-2′-Deoxyguanosine

Fàbrega

Macías

Eritja

2001

Nucleosides, Nucleotides and Nucleic Acids

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Characterization of the defect in the Escherichia coli mutT1 mutator gene

Abstract: With a probe constructed from the wild-type gene, a DNA fragment containing the entire mutT1 mutator gene was isolated and cloned into pUC18. Nucleotide sequence analysis revealed that the mutator defect was most likely due to an IS1 insertion into the wild-type gene.

Cited by 30 publications

References 15 publications

Structural and Dynamic Features of the MutT Protein in the Recognition of Nucleotides with the Mutagenic 8-Oxoguanine Base

Structural and Dynamic Features of the MutT Protein in the Recognition of Nucleotides with the Mutagenic 8-Oxoguanine Base

Critical Intracellular Ca2+ Dependence of Transient Receptor Potential Melastatin 2 (TRPM2) Cation Channel Activation

Synthesis and Properties of Oligonucleotides Containing 8-Bromo-2′-Deoxyguanosine

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