par Dupont, Julien ;Snoussi, Karim
Référence Journal of biological physics, 37, 1, page (61-68)
Publication Publié, 2011-01
Article révisé par les pairs
Résumé : Using NMR magnetization transfer from water and ammonia-catalyzed exchange of the imino protons, changes have been monitored in base-pair kinetics induced by Mg2+ in two key activity fragments r(CACCUGGCGACAGGUG) and r(GGCCAAAAGCC) of the encephalomyocarditis virus internal ribosome entry site. For r(CACCUGGCGACAGGUG), the addition of Mg2+ reveals two types of base-pairs: r(U545•A) and r(G546•C), in the first category, have lifetimes only slightly higher in the presence of Mg 2+, whereas their dissociation constants are substantially reduced. This behavior has been termed proximal. The base-pairs r(G553•C) and r(G554•C), in the second category, have lifetimes substantially higher in the presence of Mg2+, whereas their dissociation constants remain almost constant. This behavior has been termed distal. Mg2+ has a specific effect on r(CACCUGGCGACAGGUG), the magnitude of which is progressively modulated from the proximal region of the 16-mer towards its distal region. For r(GGCCAAAAGCC), an intermediate behavior is found for base-pairs r(G565•C) and r(G572•C). Their lifetimes are slightly higher in the presence of Mg2+ and their dissociation constants are significantly lower, a behavior resembling that of the 16-mer proximal region. These results indicate that Mg2+ diffusively moves around r(GGCCAAAAGCC). © 2010 Springer Science+Business Media B.V.