Yoshida A, Sun S, Piccirilli J A
Department of Biochemistry and Molecular Biology, Howard Hughes Medical Institute, The University of Chicago, Illinois 60637, USA.
Nat Struct Biol. 1999 Apr;6(4):318-21. doi: 10.1038/7551.
The Tetrahymena ribozyme is a metalloenzyme that catalyzes cleavage of oligonucleotide substrates by phosphoryl transfer. Thiophilic metal ions such as Mn2+, Zn2+ or Cd2+ rescue the >10(3)-fold inhibitory effect of sulfur substitution of the 3'-oxygen leaving group but do not effectively rescue the effect of sulfur substitution of the nonbridging pro-Sp phosphoryl oxygen. We now show that the latter effect can be fully rescued by Zn2+ or Cd2+ using a phosphorodithioate substrate, in which both the 3'-oxygen and the pro-Sp oxygen are simultaneously substituted with sulfur. These results provide the first functional evidence that metallophosphotransferases can mediate catalysis via metal ion coordination to both the leaving group and a nonbridging oxygen of the scissile phosphate.
嗜热四膜虫核酶是一种金属酶，通过磷酸转移催化寡核苷酸底物的切割。亲硫金属离子如Mn2+、Zn2+或Cd2+可挽救3'-氧离去基团硫取代产生的>10(3)倍抑制作用，但不能有效挽救非桥连亲-Sp磷酰氧硫取代的作用。我们现在表明，使用二硫代磷酸酯底物，其中3'-氧和亲-Sp氧同时被硫取代，Zn2+或Cd2+可以完全挽救后一种作用。这些结果提供了第一个功能证据，即金属磷酸转移酶可以通过金属离子与离去基团和可裂解磷酸酯的非桥连氧的配位来介导催化作用。
