3GX7

Crystal structure of the T. tengcongensis SAM-I riboswitch variant U34C/A94G mutant A6C/U7G/A87C/U88G bound with SAM

Summary for 3GX7

• Entry DOI: 10.2210/pdb3gx7/pdb
• Related: 3GX2 3GX3 3GX5 3GX6
• Descriptor: RNA (94-MER), S-ADENOSYLMETHIONINE, MAGNESIUM ION (3 entities in total)
• Functional Keywords: kink-turn, four-way junction, pseudoknot, riboswitch, rna
• Total number of polymer chains: 1
• Total formula weight: 31142.64

Authors

Montange, R.K.,Batey, R.T. (deposition date: 2009-04-01, release date: 2010-01-12, Last modification date: 2023-09-06)

Primary citation

Montange, R.K.,Mondragon, E.,van Tyne, D.,Garst, A.D.,Ceres, P.,Batey, R.T.
Discrimination between Closely Related Cellular Metabolites by the SAM-I Riboswitch.
J.Mol.Biol., 396:761-772, 2010

PubMed Abstract: The SAM-I riboswitch is a cis-acting element of genetic control found in bacterial mRNAs that specifically binds S-adenosylmethionine (SAM). We previously determined the 2.9-A X-ray crystal structure of the effector-binding domain of this RNA element, revealing details of RNA-ligand recognition. To improve this structure, variations were made to the RNA sequence to alter lattice contacts, resulting in a 0.5-A improvement in crystallographic resolution and allowing for a more accurate refinement of the crystallographic model. The basis for SAM specificity was addressed by a structural analysis of the RNA complexed to S-adenosylhomocysteine (SAH) and sinefungin and by measuring the affinity of SAM and SAH for a series of mutants using isothermal titration calorimetry. These data illustrate the importance of two universally conserved base pairs in the RNA that form electrostatic interactions with the positively charged sulfonium group of SAM, thereby providing a basis for discrimination between SAM and SAH.

PubMed: 20006621
DOI: 10.1016/j.jmb.2009.12.007

Experimental method

X-RAY DIFFRACTION (2.95 Å)