title: The extended loops of ribosomal proteins uL4 and uL22 of Escherichia coli contribute to ribosome assembly and protein translation.
abstract: Nearly half of ribosomal proteins are composed of a domain on the ribosome surface and a loop or extension that penetrates into the organelle's RNA core. Our previous work showed that ribosomes lacking the loops of ribosomal proteins uL4 or uL22 are still capable of entering polysomes. However, in those experiments we could not address the formation of mutant ribosomes, because we used strains that also expressed wild-type uL4 and uL22. Here, we have focused on ribosome assembly and function in strains in which loop deletion mutant genes are the ONLY: sources of uL4 or uL22 protein. The uL4 and uL22 loop deletions have different effects, but both mutations result in accumulation of immature particles that do not accumulate in detectable amounts in wild-type strains. Thus, our results suggest that deleting the loops creates kinetic barriers in the normal assembly pathway, possibly resulting in assembly via alternate pathway(s). Furthermore, deletion of the uL4 loop results in cold-sensitive ribosome assembly and function. Finally, ribosomes carrying either of the loop-deleted proteins responded normally to the secM translation pausing peptide, but the uL4 mutant responded very inefficiently to the cmlA(crb) pause peptide.
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
authors.forename: Marlon G
authors.initials: MG
authors.lastname: Lawrence
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
authors.forename: Md
authors.initials: M
authors.lastname: Shamsuzzaman
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
authors.forename: Maithri
authors.initials: M
authors.lastname: Kondopaka
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
authors.forename: Clarence
authors.initials: C
authors.lastname: Pascual
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
authors.forename: Janice M
authors.initials: JM
authors.lastname: Zengel
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250, USA Lindahl@umbc.edu.
authors.forename: Lasse
authors.initials: L
authors.lastname: Lindahl
mesh_terms: D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008958:Models, Molecular; D001678:Organelle Biogenesis; D011132:Polyribosomes; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000378:metabolism; D012338:RNA, Ribosomal, 23S / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D020033:Protein Isoforms; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S; D016601:RNA-Binding Proteins; D012269:Ribosomal Proteins; C497347:SecM protein, E coli; D014157:Transcription Factors; C056368:ribosomal protein L4; C489371:rplV protein, E coli