3HL2

The crystal structure of the human SepSecS-tRNASec complex

Summary for 3HL2

• Entry DOI: 10.2210/pdb3hl2/pdb
• Descriptor: O-phosphoseryl-tRNA(Sec) selenium transferase, tRNASec, (5-HYDROXY-4,6-DIMETHYLPYRIDIN-3-YL)METHYL DIHYDROGEN PHOSPHATE, ... (6 entities in total)
• Functional Keywords: selenocysteine, trnasec, sepsecs, protein-rna complex, alternative splicing, cytoplasm, protein biosynthesis, pyridoxal phosphate, selenium, transferase
• Biological source: Homo sapiens (human); More
• Cellular location: Cytoplasm : Q9HD40
• Total number of polymer chains: 5
• Total formula weight: 254128.03

Authors

Palioura, S.,Steitz, T.A.,Soll, D.,Simonovic, M. (deposition date: 2009-05-26, release date: 2009-10-06, Last modification date: 2024-11-27)

Primary citation

Palioura, S.,Sherrer, R.L.,Steitz, T.A.,Soll, D.,Simonovic, M.
The human SepSecS-tRNASec complex reveals the mechanism of selenocysteine formation.
Science, 325:321-325, 2009

PubMed 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.

PubMed: 19608919
DOI: 10.1126/science.1173755

Experimental method

X-RAY DIFFRACTION (2.81 Å)