The amino-terminal domain of pyrrolysyl-tRNA synthetase is dispensable in vitro but required for in vivo activity |
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Authors: | Herring Stephanie Ambrogelly Alexandre Gundllapalli Sarath O'Donoghue Patrick Polycarpo Carla R Söll Dieter |
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Affiliation: | Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA. |
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Abstract: | Pyrrolysine (Pyl) is co-translationally inserted into a subset of proteins in the Methanosarcinaceae and in Desulfitobacterium hafniense programmed by an in-frame UAG stop codon. Suppression of this UAG codon is mediated by the Pyl amber suppressor tRNA, tRNA(Pyl), which is aminoacylated with Pyl by pyrrolysyl-tRNA synthetase (PylRS). We compared the behavior of several archaeal and bacterial PylRS enzymes towards tRNA(Pyl). Equilibrium binding analysis revealed that archaeal PylRS proteins bind tRNA(Pyl) with higher affinity (K(D)=0.1-1.0 microM) than D. hafniense PylRS (K(D)=5.3-6.9 microM). In aminoacylation the archaeal PylRS enzymes did not distinguish between archaeal and bacterial tRNA(Pyl) species, while the bacterial PylRS displays a clear preference for the homologous cognate tRNA. We also show that the amino-terminal extension present in archaeal PylRSs is dispensable for in vitro activity, but required for PylRS function in vivo. |
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Keywords: | aaRS, aminoacyl-tRNA synthetase Pyl, pyrrolysine PylRS, pyrrolysyl-tRNA synthetase |
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