|
type |
Journal Article |
authors |
Palioura S, Sherrer RL, Steitz TA, Söll D, Simonovic M. |
title |
The human SepSecS-tRNASec complex reveals the mechanism of selenocysteine formation |
journal |
Science |
Activity |
2.9.1.2 |
Family |
2.9.1.2 |
sel |
selected |
ui |
19608919 |
year |
(2009) |
volume |
325 |
number |
5938 |
pages |
321-5 |
| |
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. |
last changed |
2010/01/12 13:20 |
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