Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
J Am Chem Soc. 2012 Mar 7;134(9):4132-41. doi: 10.1021/ja208483v. Epub 2012 Feb 22.
A multidimensional heteronuclear NMR study has demonstrated that a guanine-rich DNA oligonucleotide originating from the N-myc gene folds into G-quadruplex structures in the presence of K(+), NH(4)(+), and Na(+) ions. A monomeric G-quadruplex formed in K(+) ion containing solution exhibits three G-quartets and flexible propeller-type loops. The 3D structure with three single nucleotide loops represents a missing element in structures of parallel G-quadruplexes. The structural features together with the high temperature stability are suggestive of the specific biological role of G-quadruplex formation within the intron of the N-myc gene. An increase in K(+) ion and oligonucleotide concentrations resulted in transformation of the monomeric G-quadruplex into a dimeric form. The dimeric G-quadruplex exhibits six stacked G-quartets, parallel strand orientations, and propeller-type loops. A link between the third and the fourth G-quartets consists of two adenine residues that are flipped out to facilitate consecutive stacking of six G-quartets.
一项多维异核 NMR 研究表明，一种来源于 N-myc 基因的富含鸟嘌呤的 DNA 寡核苷酸在 K(+)、NH(4)(+) 和 Na(+) 离子存在的条件下折叠成 G-四链体结构。在含有 K(+)离子的溶液中形成的单体 G-四链体表现出三个 G-四联体和灵活的推进器型环。具有三个单核苷酸环的 3D 结构代表了平行 G-四链体结构中缺失的元素。这些结构特征以及高温稳定性表明，G-四链体在 N-myc 基因的内含子中具有特定的生物学作用。随着 K(+)离子和寡核苷酸浓度的增加，单体 G-四链体转化为二聚体形式。二聚体 G-四链体表现出六个堆叠的 G-四联体、平行链取向和推进器型环。第三和第四个 G-四联体之间的连接由两个腺嘌呤残基组成，这些残基翻转出来以促进六个 G-四联体的连续堆叠。
