Summary information and primary citation
- PDB-id
-
5t83;
DSSR-derived features in text and
JSON formats
- Class
- RNA
- Method
- X-ray (2.71 Å)
- Summary
- Structure of a guanidine-i riboswitch from s.
acidophilus
- Reference
-
Reiss CW, Xiong Y, Strobel SA (2017): "Structural
Basis for Ligand Binding to the Guanidine-I
Riboswitch." Structure, 25,
195-202. doi: 10.1016/j.str.2016.11.020.
- Abstract
- The guanidine-I riboswitch is a conserved RNA element
with approximately 2,000 known examples across four phyla
of bacteria. It exists upstream of nitrogen metabolism and
multidrug resistance transporter genes and alters
expression through the specific recognition of a free
guanidinium cation. Here we report the structure of a
guanidine riboswitch aptamer from Sulfobacillus acidophilus
at 2.7 Å resolution. Helices P1, P1a, P1b, and P2 form
a coaxial stack that acts as a scaffold for ligand binding.
A previously unidentified P3 helix docks into P1a to form
the guanidinium binding pocket, which is completely
enclosed. Every functional group of the ligand is
recognized through hydrogen bonding to guanine bases and
phosphate oxygens. Guanidinium binding is further
stabilized through cation-π interactions with guanine
bases. This allows the riboswitch to recognize guanidinium
while excluding other bacterial metabolites with a
guanidino group, including the amino acid arginine.
