Smith D R
Molecular Neurobiology Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, Republic of Singapore.
Methods Mol Biol. 1993;18:427-31. doi: 10.1385/0-89603-245-0:427.
The ability to cleave DNA at specific sites is one of the cornerstones of today's methods of DNA manipulation. Restriction endonucleases are bacterial enzymes that cleave duplex DNA at specific target sequences with the production of defined fragments. These enzymes can be purchased from the many manufacturers of biotechnology products. The nomenclature of enzymes is based on a simple system, proposed by Smith and Nathans. The name of the enzyme (such as Bam HI, Eco RI, and so forth) tells us about the origin of the enzyme, but does not give us any information about the specificity of cleavage. This has to be determined for each individual enzyme. The recognition site for most of the commonly used enzymes is a short palindromic sequence, usually of either 4, 5, or 6 bp in length, such as AGCT (for Alu I), GAATTC (for Eco RI), and so on. Each enzyme cuts the palindrome at a particular site, and two different enzymes may have the same recognition sequence, but cleave the DNA at different points within that sequence. The cleavage sites fall into three different categories, either flush (or blunt) in which the recognition site is cut in the middle, or either with 5'; or 3'; overhangs, in which case unpaired bases will be produced on both ends of the fragment. For a comprehensive review of restriction endonucleases, see Fuchs and Blakesley.
在特定位点切割DNA的能力是当今DNA操作方法的基石之一。限制性内切核酸酶是细菌酶，可在特定靶序列处切割双链DNA，产生特定片段。这些酶可以从众多生物技术产品制造商处购得。酶的命名基于Smith和Nathans提出的一个简单系统。酶的名称（如Bam HI、Eco RI等）告诉我们酶的来源，但没有提供任何关于切割特异性的信息。每种酶的特异性都必须单独确定。大多数常用酶的识别位点是一个短的回文序列，通常长度为4、5或6个碱基对，如AGCT（用于Alu I）、GAATTC（用于Eco RI）等。每种酶在特定位点切割回文序列，两种不同的酶可能具有相同的识别序列，但在该序列内的不同点切割DNA。切割位点可分为三类，要么是平端（或钝端），即识别位点在中间被切割，要么是5'或3'突出端，在这种情况下，片段两端会产生未配对的碱基。有关限制性内切核酸酶的全面综述，请参阅Fuchs和Blakesley。
