Multiple-turnover thio-ATP hydrolase and phospho-enzyme intermediate formation activities catalyzed by an RNA enzyme

摘要

Ribozymes that phosphorylate internal 2′-OH positions mimic the first mechanistic step of P-type ATPase enzymes by forming a phospho-enzyme intermediate. We previously described 2′-autophosphorylation and autothiophosphorylation by the 2PTmin3.2 ribozyme. In the present work we demonstrate that the thiophosphorylated form of this ribozyme can de-thiophosphorylate in the absence of ATPγS. Identical ionic conditions yield a thiophosphorylated strand when ATPγS is included, thus effecting a net ATPγS hydrolysis. The de-thiophosphorylation step is nearly independent of pH over the range of 6.3–8.5 and does not require a specifically folded RNA structure, but this step is greatly stimulated by transition metal ions. By monitoring thiophosphate release, we observe 29–46 ATPγS hydrolyzed per ribozyme strand in 24 h, corresponding to a turnover rate of 1.2–2.0 h⁻¹. The existence of an ATP- (or thio-ATP-)powered catalytic cycle raises the possibility of using ribozymes to transduce chemical energy into mechanical work for nucleic acid nanodevices.