Restoring species-specific posttransfer editing activity to a synthetase with a defunct editing domain

Abstract

In contrast, the isolated INS domain displays only weak editing activity and lacks tRNA sequence specificity. These results emphasize the modular nature of synthetase editing active sites and demonstrate how in evolution, a weak editing activity can be converted to a more robust state through fusion to the body of a synthetase. In this manner, a single editing module can be distributed to different synthetases, and simultaneously acquire specificity and enhanced activity.Prolyl-tRNA synthetase ͉ Saccharomyces cerevisiae

Coordination of tRNA Synthetase Active Sites for Chemical Fidelity

“…This finding is consistent with the previously published molecular dynamic simulation that the CP1 domain contributes to the cognate amino acid specificity in tryptophanyl-tRNA synthetase (37). It is also consistent with the editing domains of the class II ProRS, which have been fused or appended to the synthetic core at diverse sites (36,38).…”

“…This was also found for the class II ProRS editing domain, which is fused to a catalytic core that has a completely different fold (36,38). Surprisingly, in the case of LeuRS, this increase in discrimination was also conferred by the addition of the noncognate CP1…”

“…Significantly, kinetic measurements showed that the synthetic site has increased its discrimination to exceed 1/3000. Likewise, yeast ProRS has an inactive editing domain that has been retained in conjunction with an active site that has similarly increased amino acid discrimination (38). This is the threshold for aaRSs that has been proposed to require an editing domain to maintain fidelity (2,40).…”

Quality control despite mistranslation caused by an ambiguous genetic code

“…Such mistranslation may lead to observable cellular and disease pathologies such as cell degeneration and apoptosis in mammalian systems (19) and neurodegeneration and ataxia in mice (20). Moreover, since heritable mutations in human glycyl-tRNA synthetase and tyrosyl-tRNA synthetase genes have been directly associated with the peripheral neuropathy Charcot-Marie-Tooth (21,22), the role of the aaRSs and their editing function in maintaining translational fidelity have become areas of intense study (23)(24)(25)(26)(27)(28).…”

Degenerate Connective Polypeptide 1 (CP1) Domain from Human Mitochondrial Leucyl-tRNA Synthetase

“…Previous work showed that the N-terminal extension of S. cerevisiae ProRS (ScProRS) has low homology with the INS domain, and it is deprived of some key residues, which may be the relics of a previously functional domain. Although editing-deficient, it still contributes to the catalytic rate of the whole enzyme (39).…”