Electrostatic versus Nonelectrostatic Effects in DNA Sequence Discrimination by Divalent Ions Mg2+ and Mn2+
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- 作者：Ivá ; n Solt ; Istvá ; n Simon ; Attila G. Csá ; szá ; r ; Monika Fuxreiter
- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：June 7, 2007
- 年：2007
- 卷：111
- 期：22
- 页码：6272 - 6279
- 全文大小：85K
- 年卷期：v.111,no.22(June 7, 2007)
- ISSN：1520-5207
文摘
Mg2+ and Mn2+ ions are critical to the functioning of phosphoryl transfer enzymes, such as restrictionendonucleases. Although these ions play similar roles in the chemical steps, they govern substrate specificityvia modulating sequence discrimination by up to a factor of 105 with Mg2+ and only up to a factor of 10 withMn2+. To explain whether such diversity originates in fundamental differences in the electronic structures ofthe nucleobase-hydrated-metal ion complexes, structures and interaction energies were determined at thedensity functional (DFT) and second-order M
ller-Plesset (MP2) levels of theory. Although both metal ionsfavor identical binding sites, Mn2+ complexes exhibit greater distortions from the ideal octahedral geometryand larger variability than the corresponding Mg2+ systems. In inner-shell complexes, with direct contactbetween the metal and the nucleobase, Mg2+ is preferred over Mn2+ in the gas phase, due primarily tononelectrostatic effects. The interaction energies of the two metal ions are more similar in the outer-shellcomplexes, likely due to reduced charge transfer between the hydrated metal ion and the base moieties. Inclusionof solvation effects can amplify the relative nucleobase preferences of Mg2+ and Mn2+, indicating that bulkhydration modulates the balance between electrostatic and nonelectrostatic terms. In most cases, the basesubstitutions in solution are facilitated more by Mn2+ than by Mg2+. Electrostatic properties of the environmentwere demonstrated to have a major influence on the nucleobase preferences of the two metal ions. Overall,quantum chemical calculations suggest that the contrasting selectivity of Mg2+ and Mn2+ cofactors towardnucleobases derives from the larger flexibility of the Mn2+ complexes accompanied by the excessive polarizationand charge-transfer effects as well as less favorable solvation.
ller-Plesset (MP2) levels of theory. Although both metal ionsfavor identical binding sites, Mn2+ complexes exhibit greater distortions from the ideal octahedral geometryand larger variability than the corresponding Mg2+ systems. In inner-shell complexes, with direct contactbetween the metal and the nucleobase, Mg2+ is preferred over Mn2+ in the gas phase, due primarily tononelectrostatic effects. The interaction energies of the two metal ions are more similar in the outer-shellcomplexes, likely due to reduced charge transfer between the hydrated metal ion and the base moieties. Inclusionof solvation effects can amplify the relative nucleobase preferences of Mg2+ and Mn2+, indicating that bulkhydration modulates the balance between electrostatic and nonelectrostatic terms. In most cases, the basesubstitutions in solution are facilitated more by Mn2+ than by Mg2+. Electrostatic properties of the environmentwere demonstrated to have a major influence on the nucleobase preferences of the two metal ions. Overall,quantum chemical calculations suggest that the contrasting selectivity of Mg2+ and Mn2+ cofactors towardnucleobases derives from the larger flexibility of the Mn2+ complexes accompanied by the excessive polarizationand charge-transfer effects as well as less favorable solvation.