PMID:15867194
| Citation |
Cuzic, S and Hartmann, RK (2005) Studies on Escherichia coli RNase P RNA with Zn2+ as the catalytic cofactor. Nucleic Acids Res. 33:2464-74 |
|---|---|
| Abstract |
We demonstrate, for the first time, catalysis by Escherichia coli ribonuclease P (RNase P) RNA with Zn2+ as the sole divalent metal ion cofactor in the presence of ammonium, but not sodium or potassium salts. Hill analysis suggests a role for two or more Zn2+ ions in catalysis. Whereas Zn2+ destabilizes substrate ground state binding to an extent that precludes reliable Kd determination, Co(NH3)6(3+) and Sr2+ in particular, both unable to support catalysis by themselves, promote high-substrate affinity. Zn2+ and Co(NH3)6(3+) substantially reduce the fraction of precursor tRNA molecules capable of binding to RNase P RNA. Stimulating and inhibitory effects of Sr2+ on the ribozyme reaction with Zn2+ as cofactor could be rationalized by a model involving two Sr2+ ions (or two classes of Sr2+ ions). Both ions improve substrate affinity in a cooperative manner, but one of the two inhibits substrate conversion in a non-competitive mode with respect to the substrate and the Zn2+. A single 2'-fluoro modification at nt -1 of the substrate substantially weakened the inhibitory effect of Sr2+. Our results demonstrate that the studies on RNase P RNA with metal cofactors other than Mg2+ entail complex effects on structural equilibria of ribozyme and substrate RNAs as well as E*S formation apart from the catalytic performance. |
| Links |
PubMed PMC1088067 Online version:10.1093/nar/gki540 |
| Keywords |
Base Sequence; Catalysis; Cations, Divalent; Cobalt/chemistry; Coenzymes/chemistry; Escherichia coli/enzymology; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/metabolism; Kinetics; Molecular Sequence Data; RNA, Transfer/chemistry; RNA, Transfer/metabolism; Ribonuclease P/chemistry; Ribonuclease P/metabolism; Strontium/chemistry; Strontium/pharmacology; Zinc/chemistry |
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