3HL2 image
Entry Detail
PDB ID:
3HL2
Keywords:
Title:
The crystal structure of the human SepSecS-tRNASec complex
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2009-05-26
Release Date:
2009-10-06
Method Details:
Experimental Method:
Resolution:
2.81 Å
R-Value Free:
0.23
R-Value Work:
0.20
R-Value Observed:
0.20
Space Group:
P 31 1 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:O-phosphoseryl-tRNA(Sec) selenium transferase
Chain IDs:A, B, C, D
Chain Length:501
Number of Molecules:4
Biological Source:Homo sapiens
Polymer Type:polyribonucleotide
Description:tRNASec
Chain IDs:E
Chain Length:90
Number of Molecules:1
Biological Source:Homo sapiens
Primary Citation
The human SepSecS-tRNASec complex reveals the mechanism of selenocysteine formation.
Science 325 321 325 (2009)
PMID: 19608919 DOI: 10.1126/science.1173755

Abstact

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.

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Primary Citation of related structures