title: Assembly stoichiometry of bacterial selenocysteine synthase and SelC (tRNAsec).
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.
authors: Department of Physics and Informatics, Institute of Physics of Sao Carlos, University of Sao Paulo-USP, Sao Carlos, SP, Brazil.
authors: Livia Regina
authors: LR
authors: Manzine
authors: Vitor Hugo Balasco
authors: VH
authors: Serrão
authors: Luis Maurício Trambaioli
authors: LM
authors: da Rocha e Lima
authors: Marcos Michel
authors: MM
authors: de Souza
authors: Jefferson
authors: J
authors: Bettini
authors: Rodrigo Villares
authors: RV
authors: Portugal
authors: Marin
authors: M
authors: van Heel
authors: Otavio Henrique
authors: OH
authors: Thiemann
mesh_terms: D001483:Base Sequence; D001667:Binding, Competitive; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005454:Fluorescence Polarization; D007700:Kinetics; D046911:Macromolecular Substances / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D011485:Protein Binding; D055503:Protein Multimerization; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017279:Selenocysteine / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014166:Transferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D012329:RNA, Bacterial; D016053:RNA, Protozoan; D012346:RNA, Transfer, Amino Acyl; C112705:selenocysteinyl-tRNA; D017279:Selenocysteine; D014166:Transferases; C060600:selenium transferase