title: Interactions of the TnaC nascent peptide with rRNA in the exit tunnel enable the ribosome to respond to free tryptophan.
abstract: A transcriptional attenuation mechanism regulates expression of the bacterial tnaCAB operon. This mechanism requires ribosomal arrest induced by the regulatory nascent TnaC peptide in response to free L-tryptophan (L-Trp). In this study we demonstrate, using genetic and biochemical analyses, that in Escherichia coli, TnaC residue I19 and 23S rRNA nucleotide A2058 are essential for the ribosome's ability to sense free L-Trp. We show that the mutational change A2058U in 23S rRNA reduces the concentration dependence of L-Trp-mediated tna operon induction, whereas the TnaC I19L change suppresses this phenotype, restoring the sensitivity of the translating A2058U mutant ribosome to free L-Trp. These findings suggest that interactions between TnaC residue I19 and 23S rRNA nucleotide A2058 contribute to the creation of a regulatory L-Trp binding site within the translating ribosome.
authors.affiliation: Department of Biology, Texas A&M University, College Station, TX 77843, USA, Department of Biological Sciences, University of Alabama in Huntsville, Huntsville, AL 35899, USA, Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, Chicago, IL 60607, USA, Quantitative Proteomics Center, Department of Biological Sciences, Columbia University, New York, NY 10027, USA and Department of Biology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Allyson K
authors.initials: AK
authors.lastname: Martínez
authors.forename: Emily
authors.initials: E
authors.lastname: Gordon
authors.forename: Arnab
authors.initials: A
authors.lastname: Sengupta
authors.forename: Nitin
authors.initials: N
authors.lastname: Shirole
authors.forename: Dorota
authors.initials: D
authors.lastname: Klepacki
authors.forename: Blanca
authors.initials: B
authors.lastname: Martinez-Garriga
authors.forename: Lewis M
authors.initials: LM
authors.lastname: Brown
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Benedik
authors.forename: Charles
authors.initials: C
authors.lastname: Yanofsky
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Mankin
authors.forename: Nora
authors.initials: N
authors.lastname: Vazquez-Laslop
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Sachs
authors.forename: Luis R
authors.initials: LR
authors.lastname: Cruz-Vera
mesh_terms: D001665:Binding Sites; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D014176:Protein Biosynthesis; D012338:RNA, Ribosomal, 23S / Q000737:chemistry / Q000378:metabolism*; D012364:RNA, Transfer, Trp / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*; D014368:Tryptophanase / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D010455:Peptides; D012338:RNA, Ribosomal, 23S; D012364:RNA, Transfer, Trp; C081473:tnaC protein, E coli; D014364:Tryptophan; D014368:Tryptophanase