title: HflX is a ribosome-splitting factor rescuing stalled ribosomes under stress conditions.
abstract: Adverse cellular conditions often lead to nonproductive translational stalling and arrest of ribosomes on mRNAs. Here, we used fast kinetics and cryo-EM to characterize Escherichia coli HflX, a GTPase with unknown function. Our data reveal that HflX is a heat shock-induced ribosome-splitting factor capable of dissociating vacant as well as mRNA-associated ribosomes with deacylated tRNA in the peptidyl site. Structural data demonstrate that the N-terminal effector domain of HflX binds to the peptidyl transferase center in a strikingly similar manner as that of the class I release factors and induces dramatic conformational changes in central intersubunit bridges, thus promoting subunit dissociation. Accordingly, loss of HflX results in an increase in stalled ribosomes upon heat shock. These results suggest a primary role of HflX in rescuing translationally arrested ribosomes under stress conditions.
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Yanqing
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
authors.forename: Chandra Sekhar
authors.initials: CS
authors.lastname: Mandava
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Cao
authors.affiliation: Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Dejiu
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Ningning
authors.initials: N
authors.lastname: Li
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Yixiao
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Kaixia
authors.initials: K
authors.lastname: Mi
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Jianlin
authors.initials: J
authors.lastname: Lei
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
authors.forename: Suparna
authors.identifier: http://orcid.org/0000-0002-7124-792X
authors.initials: S
authors.lastname: Sanyal
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
mesh_terms: D020285:Cryoelectron Microscopy; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D046911:Macromolecular Substances / Q000648:ultrastructure; D008958:Models, Molecular; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure; D013312:Stress, Physiological
chemical_list: D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D019204:GTP-Binding Proteins; C535071:HflX protein, E coli