Crystallographic analysis of the Escherichia coli tRNA seleno-modification enzyme in complex with tRNA.

Acta Crystallogr F Struct Biol Commun

Graduate School of Life Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan.

Published: February 2025

The bacterial enzyme tRNA 2-selenouridine synthase (SelU) catalyzes the conversion of 5-substituted 2-thiouridine (R5S2U) to 5-substituted 2-selenouridine (R5Se2U) at the wobble positions of several tRNAs. Seleno-modification potentially regulates translation efficiency in response to selenium availability. Notably, SelU uses the 2-geranylthiouridine (R5geS2U) intermediate for sulfur removal, and this geranylthiol (geS) is a unique leaving group among tRNA-maturation enzymes. However, the underlying sequence of the SelU reaction remains unclear. Here, a crystallographic study of the Escherichia coli SelU-tRNA complex is reported. Robust and well formed SelU-tRNA crystals were obtained after several optimizations, including co-expression with tRNA and additive screening. Diffraction data were collected at a resolution of 3.10 Å using a wavelength of 1.0000 Å. The crystals belonged to space group C2, and the phase was determined by molecular replacement using the AlphaFold2-predicted SelU structure as a search model. Electron-density mapping revealed the presence of two SelU-tRNA complexes in the asymmetric unit.

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http://dx.doi.org/10.1107/S2053230X25000044DOI Listing

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