Radhakrishnan I, Patel D J
Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons of Columbia University, New York, NY 10032.
J Mol Biol. 1994 Aug 26;241(4):600-19. doi: 10.1006/jmbi.1994.1534.
The solution structure of a pyrimidine.purine.pyrimidine DNA triplex containing a novel T.CG base-triple has been determined via two and three-dimensional NMR spectroscopy and restrained molecular dynamics simulations incorporating explicit solvent and counter-ions. The T.CG triple, which expands the triplex code, is stabilized by a single hydrogen bond between the O-2 atom of thymine and the free amino proton of cytosine in the Watson-Crick C.G base-pair. This hydrogen bonding alignment produces large variations in helical twist at the dinucleotide steps involving the thymine residue. Localized structural perturbations in the purine-rich strand of the molecule are observed around the cytosine residue in the T.CG triple. Globally, the triplex resembles the solution structure of a previously solved pyrimidine.purine.pyrimidine DNA triplex containing an unusual G.TA triple. Also conserved are the sites and patterns of hydration in the two triplexes.
通过二维和三维核磁共振光谱以及结合明确溶剂和抗衡离子的受限分子动力学模拟，确定了含有新型T·CG碱基三联体的嘧啶·嘌呤·嘧啶DNA三链体的溶液结构。T·CG三联体扩展了三链体密码，它通过胸腺嘧啶的O-2原子与沃森-克里克C·G碱基对中胞嘧啶的游离氨基质子之间的单个氢键得以稳定。这种氢键排列在涉及胸腺嘧啶残基的二核苷酸步移处产生了螺旋扭曲的巨大变化。在T·CG三联体的胞嘧啶残基周围，观察到分子富含嘌呤链中的局部结构扰动。总体而言，该三链体类似于先前解析的含有不寻常G·TA三联体的嘧啶·嘌呤·嘧啶DNA三链体的溶液结构。两个三链体中的水合位点和模式也具有保守性。
