Observations on catalysis by hammerhead ribozymes are consistent with a two-divalent-metal-ion mechanism.
Significant cleavage by hammerhead ribozymes requires activation by divalent metal ions. Several models have been proposed to account for the influence of metal ions on hammerhead activity. A number of recent papers have presented data that have been interpreted as supporting a one-metal-hydroxide-ion mechanism. In addition, a solvent deuterium isotope effect has been taken as evidence against a proton transfer in the rate-limiting step of the cleavage reaction. We propose that these data are more easily explained by a two-metal-ion mechanism that does not involve a metal hydroxide, but does involve a proton transfer in the rate-limiting step.
Pontius
B W
BW
Department of Chemistry, University of Oregon, Eugene 97403-1129, USA.
Lott
W B
WB
von Hippel
P H
PH
D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium; D002384:Catalysis; D002413:Cations, Divalent; D003035:Cobalt; D018360:Crystallography, X-Ray; D007700:Kinetics; D007854:Lead; D008274:Magnesium; D008345:Manganese; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D016337:RNA, Catalytic / Q000737:chemistry* / Q000378:metabolism*; D013873:Thionucleotides
D002413:Cations, Divalent; D016337:RNA, Catalytic; D013873:Thionucleotides; D007854:Lead; D003035:Cobalt; D008345:Manganese; D008274:Magnesium; D002118:Calcium