Summary information and primary citation
- PDB-id
-
6ck5;
DSSR-derived features in text and
JSON formats
- Class
- RNA
- Method
- X-ray (2.49 Å)
- Summary
- Prpp riboswitch from t. mathranii bound to prpp
- Reference
-
Knappenberger AJ, Reiss CW, Strobel SA (2018): "Structures
of two aptamers with differing ligand specificity reveal
ruggedness in the functional landscape of RNA."
Elife, 7. doi: 10.7554/eLife.36381.
- Abstract
- Two classes of riboswitches related to the
<i>ykkC</i> guanidine-I riboswitch bind
phosphoribosyl pyrophosphate (PRPP) and guanosine
tetraphosphate (ppGpp). Here we report the co-crystal
structure of the PRPP aptamer and its ligand. We also
report the structure of the G96A point mutant that prefers
ppGpp over PRPP with a dramatic 40,000-fold switch in
specificity. The ends of the aptamer form a helix that is
not present in the guanidine aptamer and is involved in the
expression platform. In the mutant, the base of ppGpp
replaces G96 in three-dimensional space. This disrupts the
S-turn, which is a primary structural feature of the
<i>ykkC</i> RNA motif. These dramatic
differences in ligand specificity are achieved with minimal
mutations. <i>ykkC</i> aptamers are therefore a
prime example of an RNA fold with a rugged fitness
landscape. The ease with which the <i>ykkC</i>
aptamer acquires new specificity represents a striking case
of evolvability in RNA.
