Crystal structure of Nanoarchaeum equitans tyrosyl-tRNA synthetase and its aminoacylation activity toward tRNATyr with an extra guanosine residue at the 5′-terminus

tRNA(Tyr) of Nanoarchaeum equitans has a remarkable feature with an extra guanosine residue at the 5' terminus. However, the N. equitans tRNA(Tyr) mutant without extra guanosine at the 5'-end was tyrosylated by tyrosyl-tRNA synthase (TyrRS). We solved the crystal structure of N. equitans TyrRS at 2.80 A resolution. By comparing the present solved structure with the complex structures TyrRS with tRNATyr of Thermus thermophilus and Methanocaldococcus jannaschii, an arginine substitution mutant of N. equitans TyrRS at Ile200 (I200R), which is the putative closest candidate to the 5'-phosphate of C1 of N. equitans tRNA(Tyr), was prepared. The I200R mutant tyrosylated not only wild-type tRNA(Tyr) but also the tRNA without the G-1 residue. Further tyrosylation analysis revealed that the second base of the anticodon (U35), discriminator base (A73), and C1:G72 base pair are strong recognition sites. (C) 2021 Published by Elsevier Inc.

Automated summary

The tRNA(Tyr) of Nanoarchaeum equitans has a unique feature with an extra guanosine residue at the 5' terminus. Despite the absence of extra guanosine at the 5'-end, a mutant tRNA(Tyr) of N. equitans can still be tyrosylated by tyrosyl-tRNA synthase. A substitution mutant of N. equitans TyrRS at Ile200 was able to tyrosylate both wild-type tRNA(Tyr) and tRNA without the G-1 residue, with U35, A73, and C1:G72 identified as strong recognition sites through further analysis.