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RNA. 2018 Jul;24(7):926-938. doi: 10.1261/rna.066092.118. Epub 2018 Apr 12.

Structure-function analysis of Sua5 protein reveals novel functional motifs required for the biosynthesis of the universal t6A tRNA modification.

Author information

1
Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France.
2
Unité de Biologie Moléculaire du Gène chez les Extrêmophiles, Département de Microbiologie, Institut Pasteur, 75014 Paris, France.

Abstract

N6-threonyl-carbamoyl adenosine (t6A) is a universal tRNA modification found at position 37, next to the anticodon, in almost all tRNAs decoding ANN codons (where N = A, U, G, or C). t6A stabilizes the codon-anticodon interaction and hence promotes translation fidelity. The first step of the biosynthesis of t6A, the production of threonyl-carbamoyl adenylate (TC-AMP), is catalyzed by the Sua5/TsaC family of enzymes. While TsaC is a single domain protein, Sua5 enzymes are composed of the TsaC-like domain, a linker and an extra domain called SUA5 of unknown function. In the present study, we report structure-function analysis of Pyrococcus abyssi Sua5 (Pa-Sua5). Crystallographic data revealed binding sites for bicarbonate substrate and pyrophosphate product. The linker of Pa-Sua5 forms a loop structure that folds into the active site gorge and closes it. Using structure-guided mutational analysis, we established that the conserved sequence motifs in the linker and the domain-domain interface are essential for the function of Pa-Sua5. We propose that the linker participates actively in the biosynthesis of TC-AMP by binding to ATP/PPi and by stabilizing the N-carboxy-l-threonine intermediate. Hence, TsaC orthologs which lack such a linker and SUA5 domain use a different mechanism for TC-AMP synthesis.

KEYWORDS:

Sua5; TsaC; t6A37; tRNA modification; threonylcarbamoyl adenosine

PMID:
29650678
PMCID:
PMC6004061
DOI:
10.1261/rna.066092.118
[Indexed for MEDLINE]
Free PMC Article

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