Seryl-tRNA synthetase specificity for tRNASec in Bacterial Sec biosynthesis

• Published in: Biochimica et biophysica acta. Proteins and proteomics 2020-08, Vol.1868 (8), p.140438-140438, Article 140438
• Main Authors: de Freitas Fernandes, Adriano, Serrão, Vitor Hugo Balasco, Scortecci, Jéssica Fernandes, Thiemann, Otavio Henrique
• Format: Article
• Language: English
• Subjects: Protein-tRNA interaction; Selenocysteine; Seryl-tRNA synthetase; tRNA[Ser]Sec
• ISSN: 1570-9639; 1878-1454
• DOI: 10.1016/j.bbapap.2020.140438

tRNA synthetases are responsible for decoding the molecular information, from codons to amino acids. Seryl-tRNA synthetase (SerRS), besides the five isoacceptors of tRNASer, recognizes tRNA[Ser]Sec for the incorporation of selenocysteine (Sec, U) into selenoproteins. The selenocysteine synthesis pathway is known and is dependent on several protein-protein and protein-RNA interactions. Those interactions are not fully described, in particular, involving tRNA[Ser]Sec and SerRS. Here we describe the molecular interactions between the Escherichia coli Seryl-tRNA synthetase (EcSerRS) and tRNA[Ser]Sec in order to determine their specificity, selectivity and binding order, leading to tRNA aminoacylation. The dissociation constant of EcSerRS and tRNA[Ser]Sec was determined as (126 ± 20) nM. We also demonstrate that EcSerRS binds initially to tRNA[Ser]Sec in the presence of ATP for further recognition by E. coli selenocysteine synthetase (EcSelA) for Ser to Sec conversion. The proposed studies clarify the mechanism of tRNA[Ser]Sec incorporation in Bacteria as well as of other domains of life. [Display omitted] •Elucidation of the initial step in selenocysteine synthesis establishing the Seryl-tRNA synthetase as one of the checkpoints of the pathway.•Determination of the formation of Seryl-tRNA synthetase and tRNA[Ser]Sec complex by determining the dissociation constant values.•Using the dissociation constant values we determined the order of event’s and the sequence of interactions between the tRNA[Ser]Sec, Seryl-tRNA synthetase and Selenocysteine synthetase.