title: Formation of a Ternary Complex for Selenocysteine Biosynthesis in Bacteria.
abstract: The synthesis of selenocysteine-containing proteins (selenoproteins) involves the interaction of selenocysteine synthase (SelA), tRNA (tRNA(Sec)), selenophosphate synthetase (SelD, SPS), a specific elongation factor (SelB), and a specific mRNA sequence known as selenocysteine insertion sequence (SECIS). Because selenium compounds are highly toxic in the cellular environment, the association of selenium with proteins throughout its metabolism is essential for cell survival. In this study, we demonstrate the interaction of SPS with the SelA-tRNA(Sec) complex, resulting in a 1.3-MDa ternary complex of 27.0 ± 0.5 nm in diameter and 4.02 ± 0.05 nm in height. To assemble the ternary complex, SPS undergoes a conformational change. We demonstrated that the glycine-rich N-terminal region of SPS is crucial for the SelA-tRNA(Sec)-SPS interaction and selenoprotein biosynthesis, as revealed by functional complementation experiments. Taken together, our results provide new insights into selenoprotein biosynthesis, demonstrating for the first time the formation of the functional ternary SelA-tRNA(Sec)-SPS complex. We propose that this complex is necessary for proper selenocysteine synthesis and may be involved in avoiding the cellular toxicity of selenium compounds.
authors.affiliation: From the Physics and Informatics Department, Physics Institute of Sao Carlos, University of Sao Paulo - USP, CEP 13563-120 Sao Carlos, SP.
authors.forename: Ivan R
authors.initials: IR
authors.lastname: Silva
authors.affiliation: From the Physics and Informatics Department, Physics Institute of Sao Carlos, University of Sao Paulo - USP, CEP 13563-120 Sao Carlos, SP, the Physics Department, Federal University of Sao Carlos - UFSCar, 13565-905 Sao Carlos, SP, Brazil.
authors.forename: Vitor H B
authors.initials: VH
authors.lastname: Serrão
authors.affiliation: From the Physics and Informatics Department, Physics Institute of Sao Carlos, University of Sao Paulo - USP, CEP 13563-120 Sao Carlos, SP.
authors.forename: Livia R
authors.initials: LR
authors.lastname: Manzine
authors.affiliation: From the Physics and Informatics Department, Physics Institute of Sao Carlos, University of Sao Paulo - USP, CEP 13563-120 Sao Carlos, SP.
authors.forename: Lívia M
authors.initials: LM
authors.lastname: Faim
authors.affiliation: From the Physics and Informatics Department, Physics Institute of Sao Carlos, University of Sao Paulo - USP, CEP 13563-120 Sao Carlos, SP.
authors.forename: Marco T A
authors.initials: MT
authors.lastname: da Silva
authors.affiliation: From the Physics and Informatics Department, Physics Institute of Sao Carlos, University of Sao Paulo - USP, CEP 13563-120 Sao Carlos, SP.
authors.forename: Raphaela
authors.initials: R
authors.lastname: Makki
authors.affiliation: the Department of Biology/CEIS, Biosciences Institute of Rio Claro, Sao Paulo State University - UNESP, 13506-900 Rio Claro, SP, and.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Saidemberg
authors.affiliation: the Physics Department, Institute of Biosciences, Letters and Exact Sciences (IBILCE), Sao Paulo State University - UNESP, 15054-000 Sao Jose do Rio Preto, SP, Brazil.
authors.forename: Marinônio L
authors.initials: ML
authors.lastname: Cornélio
authors.affiliation: the Department of Biology/CEIS, Biosciences Institute of Rio Claro, Sao Paulo State University - UNESP, 13506-900 Rio Claro, SP, and.
authors.forename: Mário S
authors.initials: MS
authors.lastname: Palma
authors.affiliation: From the Physics and Informatics Department, Physics Institute of Sao Carlos, University of Sao Paulo - USP, CEP 13563-120 Sao Carlos, SP, thiemann@ifsc.usp.br.
authors.forename: Otavio H
authors.initials: OH
authors.lastname: Thiemann
mesh_terms: D000595:Amino Acid Sequence; D016880:Anisotropy; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005816:Genetic Complementation Test; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010770:Phosphotransferases / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D012345:RNA, Transfer, Amino Acid-Specific / Q000378:metabolism*; D017279:Selenocysteine / Q000096:biosynthesis*; D017386:Sequence Homology, Amino Acid; D017550:Spectroscopy, Fourier Transform Infrared; D014166:Transferases / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D012345:RNA, Transfer, Amino Acid-Specific; C036928:tRNA, selenocysteine-; D017279:Selenocysteine; D014166:Transferases; D010770:Phosphotransferases; C062762:selenophosphate synthetase; C060600:selenium transferase
keywords: RNA-protein interaction; bacteria; protein complex; selenocysteine; transfer RNA (tRNA)