Group II introns are Mg2+-dependent ribozymes that are considered to be the evolutionary ancestors of the eukaryotic spliceosome, thus representing an ideal model system to understand the mechanism of conversion of premature messenger RNA (mRNA) into mature mRNA. Neither in splicing nor for self-cleaving ribozymes has the role of the two Mg2+ ions been established, and even the way the nucleophile is activated is still controversial. Here we employed hybrid quantum classical QM(Car-Parrinello)/MM molecular dynamics simulations in combination with thermodynamic integration to characterize the molecular mechanism of the first and rate-determining step of the splicing process (i.e., the cleavage of the 5'-exon) catalyzed by group II intron ribozymes. Remarkably, our results show a new RNA specific dissociative mechanism in which the bulk water accepts the nucleophile's proton during its attack on the scissile phosphate. The process occurs in a single step with no Mg2+ ion activating the nucleophile, at odds with nucleases enzymes. We suggest that the novel reaction path elucidated here might be an evolutionary ancestor of the more efficient two-metal-ion mechanism found in enzymes.

Who Activates the Nucleophile in Ribozyme Catalysis? An Answer from the Splicing Mechanism of Group II Introns / Casalino, L.; Palermo, G.; Rothlisberger, U.; Magistrato, A.. - In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - ISSN 0002-7863. - 138:33(2016), pp. 10374-10377. [10.1021/jacs.6b01363]

Who Activates the Nucleophile in Ribozyme Catalysis? An Answer from the Splicing Mechanism of Group II Introns

Casalino, L.;Palermo, G.;Magistrato, A.
2016

Abstract

Group II introns are Mg2+-dependent ribozymes that are considered to be the evolutionary ancestors of the eukaryotic spliceosome, thus representing an ideal model system to understand the mechanism of conversion of premature messenger RNA (mRNA) into mature mRNA. Neither in splicing nor for self-cleaving ribozymes has the role of the two Mg2+ ions been established, and even the way the nucleophile is activated is still controversial. Here we employed hybrid quantum classical QM(Car-Parrinello)/MM molecular dynamics simulations in combination with thermodynamic integration to characterize the molecular mechanism of the first and rate-determining step of the splicing process (i.e., the cleavage of the 5'-exon) catalyzed by group II intron ribozymes. Remarkably, our results show a new RNA specific dissociative mechanism in which the bulk water accepts the nucleophile's proton during its attack on the scissile phosphate. The process occurs in a single step with no Mg2+ ion activating the nucleophile, at odds with nucleases enzymes. We suggest that the novel reaction path elucidated here might be an evolutionary ancestor of the more efficient two-metal-ion mechanism found in enzymes.
138
33
10374
10377
https://pubs.acs.org/doi/10.1021/jacs.6b01363
Casalino, L.; Palermo, G.; Rothlisberger, U.; Magistrato, A.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11767/68390
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