title: Structural insights into the assembly of the 30S ribosomal subunit in vivo: functional role of S5 and location of the 17S rRNA precursor sequence.
abstract: The in vivo assembly of ribosomal subunits is a highly complex process, with a tight coordination between protein assembly and rRNA maturation events, such as folding and processing of rRNA precursors, as well as modifications of selected bases. In the cell, a large number of factors are required to ensure the efficiency and fidelity of subunit production. Here we characterize the immature 30S subunits accumulated in a factor-null Escherichia coli strain (∆rsgA∆rbfA). The immature 30S subunits isolated with varying salt concentrations in the buffer system show interesting differences on both protein composition and structure. Specifically, intermediates derived under the two contrasting salt conditions (high and low) likely reflect two distinctive assembly stages, the relatively early and late stages of the 3' domain assembly, respectively. Detailed structural analysis demonstrates a mechanistic coupling between the maturation of the 5' end of the 17S rRNA and the assembly of the 30S head domain, and attributes a unique role of S5 in coordinating these two events. Furthermore, our structural results likely reveal the location of the unprocessed terminal sequences of the 17S rRNA, and suggest that the maturation events of the 17S rRNA could be employed as quality control mechanisms on subunit production and protein translation.
authors.affiliation: Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
authors.forename: Zhixiu
authors.initials: Z
authors.lastname: Yang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Guo
authors.forename: Simon
authors.initials: S
authors.lastname: Goto
authors.forename: Yuling
authors.initials: Y
authors.lastname: Chen
authors.forename: Ningning
authors.initials: N
authors.lastname: Li
authors.forename: Kaige
authors.initials: K
authors.lastname: Yan
authors.forename: Yixiao
authors.initials: Y
authors.lastname: Zhang
authors.forename: Akira
authors.initials: A
authors.lastname: Muto
authors.forename: Haiteng
authors.initials: H
authors.lastname: Deng
authors.forename: Hyouta
authors.initials: H
authors.lastname: Himeno
authors.forename: Jianlin
authors.initials: J
authors.lastname: Lei
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
mesh_terms: D020285:Cryoelectron Microscopy; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012335:RNA, Ribosomal / Q000032:analysis* / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054680:Ribosome Subunits, Small, Bacterial / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D012492:Salts / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D012335:RNA, Ribosomal; C092748:RbfA protein, E coli; D012269:Ribosomal Proteins; D012492:Salts; C030831:ribosomal protein S5; D020558:GTP Phosphohydrolases; C467318:RsgA protein, E coli