A CONFORMATIONAL CHANGE IN THE CATALYTIC CORE OF THE HAMMERHEAD RIBOZYME UPON CLEAVAGE OF AN RNA SUBSTRATE

Heteronuclear multidimensional NMR structural studies have been perfor med on a hammerhead ribozyme complexed with a cleaved and an uncleaved substrate, The NMR data demonstrate that the three helices surroundin g the conserved catalytic core hammerhead are stably formed in both co mplexes. Evidence is also presented that indicates that the sheared G- A base pairs in the conserved core are formed in the absence of Mg2+. The NMR structural data demonstrate that there is a significant struct ural change of the conserved core of the hammerhead ribozyme-substrate complex upon cleavage of the substrate. Molecular dynamics calculatio ns were performed to generate models of the ribozyme-cleaved substrate complex, and these results are used to help understand the mechanism of the hammerhead cleavage reaction.