Molecule of the Month: Riboswitches
Special sequences of messenger RNA can bind to regulatory molecules and affect synthesis of proteins
Flipping the Switch
Exploring the Structure
Purine-binding Riboswitches (PDB entries 1y26 and 1y27)
Riboswitches are remarkably specific for their preferred ligands, rivaling proteins for their strength and selectivity. Two similar riboswitches are shown here, one specific for guanine and the other specific for adenine (PDB entries 1y27 and 1y26 ). They have virtually identical nucleotide sequences, and fold into a virtually identical shape. The nucleotide at position 74 is the key to specificity: it forms a typical Watson-Crick base pair with the ligand, and discriminates between adenine and guanine. To take a closer look at this base pairing, click on the images here for an interactive Jmol image.
Topics for Further Discussion
- There are structures of many different riboswitches in the PDB. Can you find other examples?
- Riboswitches recognize their ligands using only the four types of bases found in RNA. Try looking closely at these structures to discover how different riboswitches recognize their different ligands.
October 2010, David Goodselldoi:10.2210/rcsb_pdb/mom_2010_10