engleski

Revealing the structure of the first plant aminoacyl-tRNA synthetase at 2.3 Å

In the process of protein translation, a proper attachment of a cognate amino acid to the appropriate tRNA requires involvement of an aminoacyl-tRNA synthetase (aaRS). Outside translation, aaRSs may exert additional non- canonical activities in diverse cellular processes. Eukaryotes and the majority of prokaryotes (with an exception of a small number of methanogenic archea) possess bacterial type of seryl-tRNA synthetase (SerRS). SerRSs are homodimers that contain a globular catalytic domain catalyzing aminoacylation and a coiled-coil tRNA binding domain needed for recognition of cognate tRNA. Even though many crystal structures of bacterial type of SerRS are known, no plant structure of SerRS was solved untill now. Here we report the first crystal structure of plant SerRS from Arabidopsis thaliana (AtSerRS) at the resolution of 2.3 Å. This is also the first crystal structure of plant aaRS. The protein crystallized in the monoclinic I 2 space group with one monomer per asymmetric unit. The final model of AtSerRS structure was refined to the values of Rwork = 0.211 and Rfree = 0.278. The monomer is composed of two domains, the tRNA binding domain and the catalytic core, well conserved among the other bacterial types of SerRS. A dimer is generated by the two-fold symmetry axis. It forms a dimer also in the solution as confirmed by SLS. Very flexible parts of the molecule lack electron density so the amino acids residues comprising Glu10-Gly12, Lys67- Ala73, Ala214-Asp220, Ser274-Thr279, Gly378-Glu384 and 437Ala-456Glu are not visible in the crystal structure. Interestingly, a unique disulphide bond between Cys213 and Cys244 of the same monomer is present in the crystal structure.

crystal structure, seryl-tRNA synthetase, Arabidopsis thaliana

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