Letai A G, Palladino M A, Fromm E, Rizzo V, Fresco J R
Department of Biochemical Sciences, Princeton University, New Jersey 08544.
Biochemistry. 1988 Dec 27;27(26):9108-12. doi: 10.1021/bi00426a007.
The binding of a variety of deoxyribo and ribo homo- and copolynucleotide complementary duplexes to agarose-linked homopolynucleotide affinity columns has been studied. The results provide information concerning the specificity of recognition of complementary base pairs of nucleic acids through a mechanism that involves triple-helix formation under physiological conditions of ionic strength, pH, and temperature. The method employed made it possible, for the first time, to survey the full range of base triplets conceivable from the canonical nucleic acid bases and, in addition, hypoxanthine and thereby to differentiate between those triplets which can and cannot form. Certain previously observed features of the stereochemistry of double-helical targets for third-strand binding are confirmed, and some unrecognized features are elaborated. These include a general requirement for clusters of purine residues in one strand, protonation of third-strand C residues, the ability of natural third-strand residues to distinguish between A.T/U and G.C base pairs, and a capacity of third-strand (unnatural) I residues to recognize all base pairs within such clusters. Thus, the basis for a third-strand binding code is demonstrated.
研究了多种脱氧核糖核酸和核糖核酸的同聚核苷酸及共聚核苷酸互补双链体与琼脂糖连接的同聚核苷酸亲和柱的结合情况。这些结果通过一种在离子强度、pH值和温度的生理条件下涉及三链螺旋形成的机制，提供了有关核酸互补碱基对识别特异性的信息。所采用的方法首次使得能够全面考察从标准核酸碱基以及次黄嘌呤中可以想象到的所有碱基三联体，并由此区分哪些三联体能够形成以及哪些不能形成。确认了先前观察到的第三链结合的双螺旋靶标立体化学的某些特征，并阐述了一些未被认识到的特征。这些特征包括一条链中嘌呤残基簇的一般要求、第三链C残基的质子化、天然第三链残基区分A.T/U和G.C碱基对的能力，以及第三链（非天然）I残基识别此类簇内所有碱基对的能力。因此，证明了第三链结合密码的基础。
