2C5S: Crystal Structure Of Bacillus Anthracis Thii, A Trna- Modifying Enzyme Containing The Predicted Rna-Binding Thump Domain

ThiI is an enzyme responsible for the formation of the modified base S(4)U (4-thiouridine) found at position 8 in some prokaryotic tRNAs. This base acts as a sensitive trigger for the response mechanism to UV exposure, providing protection against its damaging effects. We present the crystal structure of Bacillus anthracis ThiI in complex with AMP, revealing an extended tripartite architecture in which an N-terminal ferredoxin-like domain (NFLD) connects the C-terminal catalytic PP-loop pyrophosphatase domain with a THUMP domain, an ancient predicted RNA-binding domain that is widespread in all kingdoms of life. We describe the structure of the THUMP domain, which appears to be unrelated to RNA-binding domains of known structure. Mapping the conserved residues of NFLD and the THUMP domain onto the ThiI structure suggests that these domains jointly form the tRNA-binding surface. The inaccessibility of U8 in the canonical L-shaped form of tRNA, and the existence of a glycine-rich linker joining the catalytic and RNA-binding moieties of ThiI suggest that structural changes may occur in both molecules upon binding.
PDB ID: 2C5SDownload
MMDB ID: 36272
PDB Deposition Date: 2005/11/1
Updated in MMDB: 2005/12
Experimental Method:
x-ray diffraction
Resolution: 2.5  Å
Source Organism:
Similar Structures:
Biological Unit for 2C5S: dimeric; determined by author and by software (PQS)
Molecular Components in 2C5S
Label Count Molecule
Proteins (2 molecules)
Probable Thiamine Biosynthesis Protein Thii(Gene symbol: thiI)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB