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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=156065Documentos Relacionados
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