Formation of a Ternary Complex for Selenocysteine Biosynthesis in Bacteria

Author(s)

Silva, Ivan R. ^[1] ; Serrao, Vitor H. B. ^{[2, 1]} ; Manzine, Livia R. ^[1] ; Faim, Livia M. ^[1] ; da Silva, Marco T. A. ^[1] ; Makki, Raphaela ^[1] ; Saidemberg, Daniel M. ^[3] ; Cornelio, Marinonio L. ^[4] ; Palma, Marrio S. ^[3] ; Thiemann, Otavio H. ^[1]

Affiliation

^[1] Univ Sao Paulo, Phys Inst Sao Carlos, Phys & Informat Dept, BR-13563120 Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Carlos, Dept Phys, BR-13565905 Sao Carlos, SP - Brazil

^[3] Sao Paulo State Univ, Biosci Inst Rio Claro, Dept Biol CEIS, BR-13506900 Rio Claro, SP - Brazil

^[4] Sao Paulo State Univ, Inst Biosci Letters & Exact Sci IBILCE, Dept Phys, BR-15054000 Sao Jose Do Rio Preto, SP - Brazil

• Document type: Journal article
• Source: Journal of Biological Chemistry; v. 290, n. 49, p. 29178-U103, DEC 4 2015.
• Web of Science Citations: 4

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. (AU)

• FAPESP's process: 10/04429-3 - Structural Studies of Escherichia coli Selenophosphate Synthetase
• Grantee: Ivan Rosa e Silva
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 08/57910-0 - National Institute of Structural Biotechnology and Medicinal Chemistry in Infectious Diseases
• Grantee: Richard Charles Garratt
• Support Opportunities: Research Projects - Thematic Grants