NMR structure of the C-terminal domain of a tyrosyl-tRNA synthetase that functions in group I intron splicing.

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NMR structure of the C-terminal domain of a tyrosyl-tRNA synthetase that functions in group I intron splicing.

NMR structure of the C-terminal domain of a tyrosyl-tRNA synthetase that functions in group I intron splicing.

Biochemistry. 2011 Mar 25;

Authors: Paukstelis PJ, Chari N, Lambowitz AM, Hoffman DW

The mitochondrial tyrosyl-tRNA synthetases (mt TyrRSs) of Pezizomycotina fungi are bifunctional proteins that aminoacylate mitochondrial tRNATyr and are structure-stabilizing splicing cofactors for group I introns. Studies with the Neurospora crassa synthetase (CYT-18 protein) showed that splicing activity is dependent upon Pezizomycotina-specific structural adaptations that form a distinct group I intron-binding site in the N-terminal catalytic domain. Although CYT-18's C-terminal domain also binds group I introns, it has been intractable to X-ray crystallography in the full-length protein. Here, we determined an NMR structure of the isolated C-terminal domain of the Aspergillus nidulans mt TyrRS, which is closely related to but smaller than CYT-18's. The structure shows an S4 fold like that of bacterial TyrRSs, but with novel features, including three Pezizomycontia-specific insertions. 15N-1H two-dimensional NMR showed that C-terminal domains of the full-length A. nidulans and Geobacillus stearothermophilus synthetases do not tumble independently in solution, suggesting restricted orientations. Modeling onto a CYT-18/group I intron co-crystal structure indicates that the C-terminal domains of both subunits of the homodimeric protein bind different ends of the intron RNA, with one C-terminal domain having to undergo a large shift on its flexible linker to bind tRNATyr or the intron RNA on either side of the catalytic domain. The modeling suggests that the C-terminal domain acts together with the N-terminal domain to clamp parts of the intron's catalytic core, that at least one C-terminal domain insertion functions in group I intron binding, and that some C-terminal domain regions bind both tRNATyr and group I intron RNAs.

PMID: 21438536 [PubMed - as supplied by publisher]



Source: PubMed