3HL2: The crystal structure of the human SepSecS-tRNASec complex

Citation:
Abstract
Selenocysteine is the only genetically encoded amino acid in humans whose biosynthesis occurs on its cognate transfer RNA (tRNA). O-Phosphoseryl-tRNA:selenocysteinyl-tRNA synthase (SepSecS) catalyzes the final step of selenocysteine formation by a poorly understood tRNA-dependent mechanism. The crystal structure of human tRNA(Sec) in complex with SepSecS, phosphoserine, and thiophosphate, together with in vivo and in vitro enzyme assays, supports a pyridoxal phosphate-dependent mechanism of Sec-tRNA(Sec) formation. Two tRNA(Sec) molecules, with a fold distinct from other canonical tRNAs, bind to each SepSecS tetramer through their 13-base pair acceptor-TPsiC arm (where Psi indicates pseudouridine). The tRNA binding is likely to induce a conformational change in the enzyme's active site that allows a phosphoserine covalently attached to tRNA(Sec), but not free phosphoserine, to be oriented properly for the reaction to occur.
PDB ID: 3HL2Download
MMDB ID: 77185
PDB Deposition Date: 2009/5/26
Updated in MMDB: 2009/10
Experimental Method:
x-ray diffraction
Resolution: 2.81  Å
Source Organism:
Similar Structures:
Biological Unit for 3HL2: pentameric; determined by author
Molecular Components in 3HL2
Label Count Molecule
Proteins (4 molecules)
4
O-phosphoseryl-trna(sec) Selenium Transferase(Gene symbol: SEPSECS)
Molecule annotation
Nucleotide(1 molecule)
1
Trnasec
Molecule annotation
Chemicals (12 molecules)
1
4
2
4
3
4
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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