title: The effects of disruptions in ribosomal active sites and in intersubunit contacts on ribosomal degradation in Escherichia coli.
abstract: Although ribosomes are very stable under most conditions, ribosomal degradation does occur in diverse groups of organisms in response to specific stresses or environmental conditions. While non-functional ribosome decay (NRD) in yeast is well characterized, very little is known of the mechanisms that initiate ribosomal degradation in bacteria. Here we test ribosome degradation in growing Escherichia coli expressing mutant ribosomes. We found that mutations in the 16S rRNA decoding centre (G530U and A1492C) and 23S rRNA active site (A2451G) do not lead to ribosomal degradation. In contrast, 23S rRNA mutation U2585A causes degradation of both the large and small ribosomal subunits in E. coli. We further tested mutations in 23S rRNA, which disrupt ribosomal intersubunit bridges B2a and B3. Deletion of helix 69 of 23S rRNA and the point mutation A1912G in the same helix did not destabilize ribosomes, while expression of mutations A1919G in H69 and A1960G in H71 led to degradation of both mutant and wild-type ribosomes. Our results suggest an actively induced mechanism requiring de novo protein synthesis for ribosomal degradation in E. coli, which degrades both structurally inactive and active ribosomes.
authors.affiliation: Institute of Technology, Univeristy of Tartu, Nooruse 1, Tartu, 50411, Estonia.
authors.forename: Anton
authors.initials: A
authors.lastname: Paier
authors.affiliation: Institute of Molecular and Cellular Biology, University of Tartu, Riia 23, Tartu, 51010, Estonia.
authors.forename: Margus
authors.initials: M
authors.lastname: Leppik
authors.affiliation: Institute of Technology, Univeristy of Tartu, Nooruse 1, Tartu, 50411, Estonia.
authors.forename: Aksel
authors.initials: A
authors.lastname: Soosaar
authors.affiliation: Institute of Technology, Univeristy of Tartu, Nooruse 1, Tartu, 50411, Estonia.
authors.forename: Tanel
authors.initials: T
authors.lastname: Tenson
authors.affiliation: Institute of Technology, Univeristy of Tartu, Nooruse 1, Tartu, 50411, Estonia.
authors.forename: Ülo
authors.initials: Ü
authors.lastname: Maiväli
mesh_terms: D020134:Catalytic Domain; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D009154:Mutation; D055550:Protein Stability; D020871:RNA Stability; D012336:RNA, Ribosomal, 16S / Q000378:metabolism*; D012338:RNA, Ribosomal, 23S / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S