Unified two-metal mechanism of RNA synthesis and degradation by RNA polymerase

AUTOR(ES)

Sosunov, Vasily

FONTE

Oxford University Press

RESUMO

In DNA-dependent RNA polymerases, reactions of RNA synthesis and degradation are performed by the same active center (in contrast to DNA polymerases in which they are separate). We propose a unified catalytic mechanism for multisubunit RNA polymerases based on the analysis of its 3′–5′ exonuclease reaction in the context of crystal structure. The active center involves a symmetrical pair of Mg2+ ions that switch roles in synthesis and degradation. One ion is retained permanently and the other is recruited ad hoc for each act of catalysis. The weakly bound Mg2+ is stabilized in the active center in different modes depending on the type of reaction: during synthesis by the β,γ-phosphates of the incoming substrate; and during hydrolysis by the phosphates of a non-base-paired nucleoside triphosphate. The latter mode defines a transient, non-specific nucleoside triphosphate-binding site adjacent to the active center, which may serve as a gateway for polymerization of substrates.

Documentos Relacionados

• Two-metal ion mechanism of RNA cleavage by HIV RNase H and mechanism-based design of selective HIV RNase H inhibitors
• A two-metal ion mechanism operates in the hammerhead ribozyme-mediated cleavage of an RNA substrate
• Mapping the triphosphatase active site of baculovirus mRNA capping enzyme LEF4 and evidence for a two-metal mechanism
• A general two-metal-ion mechanism for catalytic RNA.
• Temperature-sensitive RNA polymerase mutants with altered subunit synthesis and degradation.