Download MendeleyMechanistic basis for PYROXD1-mediated protection of the human tRNA ligase complex against oxidative inactivation.
Loeff, L., Kroupova, A., Asanovic, I., Boneberg, F.M., Pfleiderer, M.M., Riermeier, L., Leitner, A., Ferdigg, A., Ackle, F., Martinez, J., Jinek, M.(2025) Nat Struct Mol Biol
- PubMed: 40069351
- DOI: https://doi.org/10.1038/s41594-025-01516-6
- Primary Citation of Related Structures:
8ORJ - PubMed Abstract:
The metazoan tRNA ligase complex (tRNA-LC) has essential roles in tRNA biogenesis and unfolded protein response. Its catalytic subunit RTCB contains a conserved active-site cysteine that is susceptible to metal ion-induced oxidative inactivation. The flavin-containing oxidoreductase PYROXD1 preserves the activity of human tRNA-LC in a NAD(P)H-dependent manner, but its protective mechanism remains elusive. Here, we report a cryogenic electron microscopic structure of the human RTCB-PYROXD1 complex, revealing that PYROXD1 directly interacts with the catalytic center of RTCB through its carboxy-terminal tail. NAD(P)H binding and FAD reduction allosterically control PYROXD1 activity and RTCB recruitment, while reoxidation of PYROXD1 enables timed release of RTCB. PYROXD1 interaction is mutually exclusive with Archease-mediated RTCB guanylylation, and guanylylated RTCB is intrinsically protected from oxidative inactivation. Together, these findings provide a mechanistic framework for the protective function of PYROXD1 that maintains the activity of the tRNA-LC under aerobic conditions.
- Department of Biochemistry, University of Zurich, Zurich, Switzerland.
Organizational Affiliation:
