Download MendeleyThe human SepSecS-tRNASec complex reveals the mechanism of selenocysteine formation.
Palioura, S., Sherrer, R.L., Steitz, T.A., Soll, D., Simonovic, M.(2009) Science 325: 321-325
- PubMed: 19608919
- DOI: https://doi.org/10.1126/science.1173755
- Primary Citation of Related Structures:
3HL2 - 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.
Organizational Affiliation:
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
