Abstract:
:To test whether the Y-shaped conformation of the hammerhead ribozyme is maintained throughout the catalytic pathway, the cleavage properties of circular substrates which bind the ribozyme through helices I and II were determined. Constraining the position of helices I and II in this manner did not significantly alter the rate constant for cleavage, consistent with no large rearrangement of the helices occurring during catalysis. Unexpectedly, the "internal" equilibrium between the cleavage and ligation reactions for the circular hammerheads was shifted further toward cleavage. This effect was due to the rate of ligation of the circular substrate being slower than the corresponding linear substrate. The temperature dependence of the internal equilibrium of the circular substrate revealed that although restricting the flexibility of the hammerhead reduced the favorable entropy change associated with cleavage as expected, the unfavorable enthalpy change was reduced as well, resulting in greater overall cleavage.
journal_name
Biochemistryjournal_title
Biochemistryauthors
Stage-Zimmermann TK,Uhlenbeck OCdoi
10.1021/bi980307zsubject
Has Abstractpub_date
1998-06-30 00:00:00pages
9386-93issue
26eissn
0006-2960issn
1520-4995pii
bi980307zjournal_volume
37pub_type
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