An ancient type of MnmA protein is an iron-sulfur cluster-dependent sulfurtransferase for tRNA anticodons
- 1 Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST);
- 2 Faculty of Agriculture, Department of Applied Biochemistry and Food Science, Saga University;
- 3 Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo
- ↵* Corresponding author; email: naoki-shigi{at}aist.go.jp
Abstract
Transfer RNA (tRNA) is an adaptor molecule indispensable for assigning amino acids to codons on mRNA during protein synthesis. 2-thiouridine (s2U) derivatives in the anticodons (position 34) of tRNAs for glutamate, glutamine, and lysine are post-transcriptional modifications essential for precise and efficient codon recognition in all organisms. s2U34 is introduced either by [1] bacterial MnmA / eukaryote mitochondrial Mtu1 or [2] eukaryote cytosolic Ncs6 / archaeal NcsA, and the latter enzymes possess iron-sulfur (Fe-S) cluster. Here, we report identification of novel-type MnmA homologs containing three conserved Cys residues, which could support Fe-S cluster binding and catalysis, in a broad range of bacteria, including thermophiles, Cyanobacteria, Mycobacteria, Actinomyces, Clostridium, and Helicobacter. Using EPR spectroscopy, we revealed that Thermus thermophilus MnmA (TtMnmA) contains an oxygen-sensitive [4Fe-4S]-type cluster. Efficient in vitro formation of s2U34 in tRNALys and tRNAGln by holo-TtMnmA occurred only under anaerobic conditions. Mutational analysis of TtMnmA suggested that the Fe-S cluster is coordinated by the three conserved Cys residues (Cys105, Cys108, and Cys200), and is essential for its activity. Evolutionary scenarios for the sulfurtransferases, including the Fe-S cluster containing Ncs6/NcsA s2U thiouridylases and several distantly related sulfurtransferases, are proposed.
Keywords
- Received September 6, 2019.
- Accepted December 1, 2019.
- Published by Cold Spring Harbor Laboratory Press for the RNA Society
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