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Updated: May 14, 2026

Utilizing Thermal Shift Assay to Probe Substrate Binding to Selenoprotein O
Published on: August 9, 2024
Assembly stoichiometry of bacterial selenocysteine synthase and SelC (tRNAsec)
Livia Regina Manzine1, Vitor Hugo Balasco Serrão, Luis Maurício Trambaioli da Rocha e Lima
1Department of Physics and Informatics, Institute of Physics of Sao Carlos, University of Sao Paulo-USP, Sao Carlos, SP, Brazil.
Abstract:
In bacteria selenocysteyl-tRNA(sec) (SelC) is synthesized by selenocysteine synthase (SelA). Here we show by fluorescence anisotropy binding assays and electron microscopical symmetry analysis that the SelA-tRNA(sec) binding stoichiometry is of one tRNA(sec) molecule per SelA monomer (1:1) rather than the 1:2 value proposed previously. Negative stain transmission electron microscopy revealed a D5 pointgroup symmetry for the SelA-tRNA(sec) assembly both with and without tRNA(sec) bound. Furthermore, SelA can associate forming a supramolecular complex of stacked decamer rings, which does not occur in the presence of tRNA(sec). We discuss the structure-function relationships of these assemblies and their regulatory role in bacterial selenocysteyl-tRNA(sec) synthesis.
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