Luke P A, McCallum S A, Halford S E
Anglian Biotechnology Ltd., Colchester, U.K.
Gene Amplif Anal. 1987;5:185-207.
Type II restriction endonucleases have attracted attention for two main reasons: firstly, their many applications in the dissection of DNA and in the construction of novel DNA molecules; secondly, as systems for studying the interactions of proteins with specific DNA sequences. With respect to the latter, the EcoR I restriction endonuclease has been examined in greater depth than any other type II enzyme [1-3]. However, the EcoR I enzyme has a major disadvantage as a system for studying DNA-protein interactions: the protein has a remarkably low solubility. The solutions in which EcoR I shows maximal activity, and also affinity for its recognition site, are saturated at less than 0.5 microM of this protein [4]. Consequently, many techniques that have been developed to study protein-ligand interactions but which require high concentrations of the protein in solution, such as NMR spectroscopy, cannot be used on EcoR I. But this drawback does not apply to all type II restriction enzymes. A different enzyme, the EcoR V restriction endonuclease [5-7], has special advantages as a system for studying DNA-protein interactions. In particular, this is the only type II restriction enzyme (apart from EcoR I [3]) for which crystals of the protein have been reported [7].
II型限制性内切核酸酶因其两个主要原因而备受关注：其一，它们在DNA剖析和新型DNA分子构建中有许多应用；其二，作为研究蛋白质与特定DNA序列相互作用的系统。就后者而言，EcoR I限制性内切核酸酶比任何其他II型酶都得到了更深入的研究[1 - 3]。然而，作为研究DNA - 蛋白质相互作用的系统，EcoR I酶有一个主要缺点：该蛋白质的溶解度极低。EcoR I表现出最大活性以及对其识别位点的亲和力时的溶液，在该蛋白质浓度低于0.5微摩尔时就达到饱和[4]。因此，许多已开发用于研究蛋白质 - 配体相互作用但需要溶液中高浓度蛋白质的技术，如核磁共振光谱法，不能用于EcoR I。但这一缺点并不适用于所有II型限制性酶。一种不同的酶，EcoR V限制性内切核酸酶[5 - 7]，作为研究DNA - 蛋白质相互作用的系统具有特殊优势。特别是，这是唯一一种（除了EcoR I [3]）已报道有蛋白质晶体的II型限制性酶[7]。
