title: The polypeptide tunnel system in the ribosome and its gating in erythromycin resistance mutants of L4 and L22.
abstract: Variations in the inner ribosomal landscape determining the topology of nascent protein transport have been studied by three-dimensional cryo-electron microscopy of erythromycin-resistant Escherichia coli 70S ribosomes. Significant differences in the mouth of the 50S subunit tunnel system visualized in the present study support a simple steric-hindrance explanation for the action of the drug. Examination of ribosomes in different functional states suggests that opening and closing of the main tunnel are dynamic features of the large subunit, possibly accompanied by changes in the L7/L12 stalk region. The existence and dynamic behavior of side tunnels suggest that ribosomal proteins L4 and L22 might be involved in the regulation of a multiple exit system facilitating cotranslational processing (or folding or directing) of nascent proteins.
authors.affiliation: Wadsworth Center, State University of New York at Albany, P.O. Box 509, Albany, NY 12201, USA.
authors.forename: I S
authors.initials: IS
authors.lastname: Gabashvili
authors.forename: S T
authors.initials: ST
authors.lastname: Gregory
authors.forename: M
authors.initials: M
authors.lastname: Valle
authors.forename: R
authors.initials: R
authors.lastname: Grassucci
authors.forename: M
authors.initials: M
authors.lastname: Worbs
authors.forename: M C
authors.initials: MC
authors.lastname: Wahl
authors.forename: A E
authors.initials: AE
authors.lastname: Dahlberg
authors.forename: J
authors.initials: J
authors.lastname: Frank
mesh_terms: D004352:Drug Resistance, Microbial; D004917:Erythromycin / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D008024:Ligands; D008958:Models, Molecular; D009154:Mutation; D020653:Peptide Elongation Factor G / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D020836:Protein Structure, Quaternary; D012343:RNA, Transfer / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D008024:Ligands; D020653:Peptide Elongation Factor G; D010455:Peptides; D012269:Ribosomal Proteins; C056368:ribosomal protein L4; D004917:Erythromycin; D012343:RNA, Transfer