title: Kinetic properties of Escherichia coli ribosomes with altered forms of S12.
abstract: E. coli ribosomes with alterations in S12 leading to streptomycin resistance (SmR), dependence (SmD) and pseudodependence (SmP) were studied with the quench-flow technique. Kinetic changes at the various steps of the elongation cycle were identified. The rate of hydrolysis of GTP in the ternary complex in the ribosomal A-site is decreased drastically in SmD and moderately in SmP in relation to wild-type ribosomes. Addition of streptomycin restores much of the wild-type behaviour. The SmD, SmP and SmR ribosomes have an enhanced GTP-hydrolysis idling reaction on EF-Tu, which is correlated with how aggressive proofreaders these ribosomes are in steady-state assays. We use our in vitro findings to discuss the in vivo physiology of these mutants as well as mechanistic features of E. coli translation.
authors.affiliation: University of Uppsala, Department of Molecular Biology, Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Bilgin
authors.forename: F
authors.initials: F
authors.lastname: Claesens
authors.forename: H
authors.initials: H
authors.lastname: Pahverk
authors.forename: M
authors.initials: M
authors.lastname: Ehrenberg
mesh_terms: D004926:Escherichia coli / Q000378:metabolism; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D009154:Mutation; D010441:Peptide Chain Elongation, Translational; D010444:Peptide Elongation Factor Tu / Q000378:metabolism; D010458:Peptidyl Transferases / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure; D013307:Streptomycin / Q000494:pharmacology
chemical_list: D012269:Ribosomal Proteins; C034212:ribosomal protein S12; D006160:Guanosine Triphosphate; D010458:Peptidyl Transferases; D020963:GTP Phosphohydrolase-Linked Elongation Factors; D010444:Peptide Elongation Factor Tu; D013307:Streptomycin