EC Number   |
Metals/Ions |
Reference |
|---|
   2.7.7.72 | Mg2+ |
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction |
722263, 722982 |
| 2.7.7.72 | Mg2+ |
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction. The Mg2+ ions are also required for the diposphorolysis reaction, overview |
722982 |
| 2.7.7.72 | Mg2+ |
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction. The Mg2+ ions are also required for the diposphorolysis reaction, overview. With tRNA-A76 as the substrate in the reverse reacction, only Mg2+ is catalytically competent |
722982 |
| 2.7.7.72 | Mg2+ |
required |
761296 |
| 2.7.7.72 | Mg2+ |
two metal ions are bound to the two catalytically important carboxylates. The first metal ion deprotonates the 3'-OH group of the tRNA primer and activates the resulting 3'-O for an attack at the a-phosphate of the incoming nucleotide. The second metal ion stabilizes the triphosphate moiety of the NTP and facilitates the leaving of the pyrophosphate group, overview |
721997 |
| 2.7.7.72 | Mn2+ |
while Mn2+ is incompetent for diphosphorolysis of tRNA-A76, it promotes a more rapid forward synthesis of tRNA-A76 than even the Mg2+ ion |
722982 |
| 2.7.7.72 | more |
Mn2+ cannot substitute for Mg2+ |
722263 |
| 2.7.7.72 | more |
the nature of the divalent metal ions can influence the positioning of diphosphate in the active site |
722982 |
| 2.7.7.72 | more |
the nature of the divalent metal ions can influence the positioning of diphosphate in the active site. tRNAs ending in C75 and C74, in contrast to tRNA A76, are also active with other divalent metal ions tan Mg2+, albeit less efficient due to accumulation of unreacted tRNA substrate. Diphosphorolysis of tRNA-C75 proceeds the farthest with Mg2+, followed by Co2+, and by Mn2+ and Ni2+. Pyrophosphorolysis of tRNA-C74 also proceeds the farthest with Mg2+, but it is followed by Mn2+ and Co2+ and followed by Ni2+. While the preference of divalent metal ions varies among the three reactions, it also differs from that required for the forward A76 addition. While Ca2+ and Pb2+ fail to promote diphosphorolysis of all three tRNA substrates, they also fail to promote forward synthesis of tRNA-A76 for EcCCA |
722982 |
| 2.7.7.72 | Zn2+ |
it is inert for diphosphorolysis of tRNAA76, but it is active in the forward synthesis of this tRNA |
722982 |
