title: The cryo-EM structure of YjeQ bound to the 30S subunit suggests a fidelity checkpoint function for this protein in ribosome assembly.
abstract: Recent work suggests that bacterial YjeQ (RsgA) participates in the late stages of assembly of the 30S subunit and aids the assembly of the decoding center but also binds the mature 30S subunit with high affinity. To determine the function and mechanisms of YjeQ in the context of the mature subunit, we determined the cryo-EM structure of the fully assembled 30S subunit in complex with YjeQ at 5.8-Å resolution. We found that binding of YjeQ stabilizes helix 44 into a conformation similar to that adopted by the subunit during proofreading. This finding indicates that, along with acting as an assembly factor, YjeQ has a role as a checkpoint protein, consisting of testing the proofreading ability of the 30S subunit. The structure also informs the mechanism by which YjeQ implements the release from the 30S subunit of a second assembly factor, called RbfA. Finally, it reveals how the 30S subunit stimulates YjeQ GTPase activity and leads to release of the protein. Checkpoint functions have been described for eukaryotic ribosome assembly factors; however, this work describes an example of a bacterial assembly factor that tests a specific translation mechanism of the 30S subunit.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada L8S4K1.|Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, ON, Canada L8S4K1.
authors.forename: Aida
authors.initials: A
authors.lastname: Razi
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada L8S4K1.
authors.forename: Alba
authors.initials: A
authors.lastname: Guarné
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada L8S4K1; ortegaj@mcmaster.ca.|Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, ON, Canada L8S4K1.
authors.forename: Joaquin
authors.initials: J
authors.lastname: Ortega
mesh_terms: D020285:Cryoelectron Microscopy; D048168:Escherichia coli K12 / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism; D054680:Ribosome Subunits, Small, Bacterial / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D029968:Escherichia coli Proteins; C092748:RbfA protein, E coli; D012269:Ribosomal Proteins; D020558:GTP Phosphohydrolases; C467318:RsgA protein, E coli
keywords: 30S subunit; RsgA protein; YjeQ protein; cryo-electron microscopy; ribosome assembly