文章基本信息

标题：Recognition and catalysis in nucleic acid chemistry.
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作者：R Breslow ; R Xu
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1993
卷号：90
期号：4
页码：1201-1207
DOI：10.1073/pnas.90.4.1201
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The enzyme ribonuclease A catalyzes the cleavage of RNA, using the imidazole groups of histidine-12 and histidine-119 as its principal catalytic groups. Model studies show that RNA can be cleaved by imidazole buffer itself and that, as in the enzyme, a bell-shaped pH vs. rate profile is seen. This indicates that one imidazole functions as a base, while the other, as the imidazolium ion, functions as an acid. However, in contrast to the enzymatic case, the simple model uses the imidazoles in sequential, rather than simultaneous, bifunctional catalysis. Mechanistic studies on this reaction and on the reactions of simple dinucleotides catalyzed by imidazole and other buffers establish the details of the process. The results let us propose a mechanism for the enzymatic process different from the standard one; they also stimulated us to design an improved mimic of the enzyme that uses a mechanism like that proposed for the enzyme. Critical to the mechanistic studies is observation of the rearrangement of normal 3',5'' RNA nucleotides to the 2',5'' isomers. This led us to investigate the properties of DNA isomers in which a 2',5'' link also replaces the normal 3',5'' one. The results indicate that poor base stacking in a double helix with such links makes them less suitable as genetic units.