Barton J K, Basile L A, Paranawithana S R
J Biol Chem. 1982 Jul 25;257(14):7911-4.
We have determined that the restriction endonuclease Eco RI contains 1.0 +/- 0.1 eq of zinc/monomeric enzyme. DNA cleavage by Eco RI is inhibited by ortho-phenanthroline after preincubation of the enzyme with the chelating agent. A similar inhibition by the nonchelating meta-phenanthroline is not seen. The sensitivity of the inhibition by the neutral ligand ortho-phenanthroline to preincubation is consistent with the tightly bound and inaccessible nature of the metal site. Extensive dialysis against the ortho-phenanthroline inhibitor leads to the release of the bound metal with the concomitant loss of enzyme activity. The tightly bound Zn2+ cation, then, appears to be necessary for enzyme function. The finding of zinc in Eco RI further illustrates the ubiquity of Zn2+ to DNA-protein complexes.
我们已经确定，限制性内切酶Eco RI每个单体酶含有1.0±0.1当量的锌。在用螯合剂对该酶进行预孵育后，邻菲罗啉会抑制Eco RI对DNA的切割。未观察到非螯合性的间菲罗啉有类似的抑制作用。中性配体邻菲罗啉的抑制作用对预孵育的敏感性与金属位点紧密结合且难以接近的性质一致。用邻菲罗啉抑制剂进行广泛透析会导致结合的金属释放，同时酶活性丧失。因此，紧密结合的Zn2+阳离子似乎是酶发挥功能所必需的。在Eco RI中发现锌进一步说明了Zn2+在DNA - 蛋白质复合物中普遍存在。
