title: Quaternary structure of the yeast Arc1p-aminoacyl-tRNA synthetase complex in solution and its compaction upon binding of tRNAs.
abstract: In the yeast Saccharomyces cerevisiae, the aminoacyl-tRNA synthetases (aaRS) GluRS and MetRS form a complex with the auxiliary protein cofactor Arc1p. The latter binds the N-terminal domains of both synthetases increasing their affinity for the transfer-RNA (tRNA) substrates tRNA(Met) and tRNA(Glu). Until now, structural information was available only on the enzymatic domains of the individual aaRSs but not on their complexes with associated cofactors. We have analysed the yeast Arc1p-complexes in solution by small-angle X-ray scattering (SAXS). The ternary complex of MetRS and GluRS with Arc1p, displays a peculiar extended star-like shape, implying possible flexibility of the complex. We reconstituted in vitro a pentameric complex and demonstrated by electrophoretic mobility shift assay that the complex is active and contains tRNA(Met) and tRNA(Glu), in addition to the three protein partners. SAXS reveals that binding of the tRNAs leads to a dramatic compaction of the pentameric complex compared to the ternary one. A hybrid low-resolution model of the pentameric complex is constructed rationalizing the compaction effect by the interactions of negatively charged tRNA backbones with the positively charged tRNA-binding domains of the synthetases.
authors.affiliation: Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Koehler
authors.forename: Adam
authors.initials: A
authors.lastname: Round
authors.forename: Hannes
authors.initials: H
authors.lastname: Simader
authors.forename: Dietrich
authors.initials: D
authors.lastname: Suck
authors.forename: Dmitri
authors.initials: D
authors.lastname: Svergun
mesh_terms: D024202:Electrophoretic Mobility Shift Assay; D005975:Glutamate-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism; D008718:Methionine-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012352:RNA, Transfer, Glu / Q000737:chemistry* / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000737:chemistry* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: C102145:ARC1 protein, S cerevisiae; D012352:RNA, Transfer, Glu; D012358:RNA, Transfer, Met; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D008718:Methionine-tRNA Ligase; D005975:Glutamate-tRNA Ligase