Publication Date:
2013-07-16
Description:
Selenocysteine (Sec) is translationally incorporated into proteins in response to the UGA codon. The tRNA specific to Sec (tRNA Sec ) is first ligated with serine by seryl-tRNA synthetase (SerRS). In the present study, we determined the 3.1 Å crystal structure of the tRNA Sec from the bacterium Aquifex aeolicus , in complex with the heterologous SerRS from the archaeon Methanopyrus kandleri . The bacterial tRNA Sec assumes the L-shaped structure, from which the long extra arm protrudes. Although the D-arm conformation and the extra-arm orientation are similar to those of eukaryal/archaeal tRNA Sec s, A. aeolicus tRNA Sec has unique base triples, G14:C21:U8 and C15:G20a:G48, which occupy the positions corresponding to the U8:A14 and R15:Y48 tertiary base pairs of canonical tRNAs. Methanopyrus kandleri SerRS exhibited serine ligation activity toward A. aeolicus tRNA Sec in vitro . The SerRS N-terminal domain interacts with the extra-arm stem and the outer corner of tRNA Sec . Similar interactions exist in the reported tRNA Ser and SerRS complex structure from the bacterium Thermus thermophilus . Although the catalytic C-terminal domain of M. kandleri SerRS lacks interactions with A. aeolicus tRNA Sec in the present complex structure, the conformational flexibility of SerRS is likely to allow the CCA terminal region of tRNA Sec to enter the SerRS catalytic site.
Print ISSN:
0305-1048
Electronic ISSN:
1362-4962
Topics:
Biology
