title: Accuracy of initial codon selection by aminoacyl-tRNAs on the mRNA-programmed bacterial ribosome.
abstract: We used a cell-free system with pure Escherichia coli components to study initial codon selection of aminoacyl-tRNAs in ternary complex with elongation factor Tu and GTP on messenger RNA-programmed ribosomes. We took advantage of the universal rate-accuracy trade-off for all enzymatic selections to determine how the efficiency of initial codon readings decreased linearly toward zero as the accuracy of discrimination against near-cognate and wobble codon readings increased toward the maximal asymptote, the d value. We report data on the rate-accuracy variation for 7 cognate, 7 wobble, and 56 near-cognate codon readings comprising about 15% of the genetic code. Their d values varied about 400-fold in the 200-80,000 range depending on type of mismatch, mismatch position in the codon, and tRNA isoacceptor type. We identified error hot spots (d = 200) for U:G misreading in second and U:U or G:A misreading in third codon position by His-tRNA(His) and, as also seen in vivo, Glu-tRNA(Glu). We suggest that the proofreading mechanism has evolved to attenuate error hot spots in initial selection such as those found here.
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden.
authors.forename: Jingji
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden.
authors.forename: Ka-Weng
authors.initials: KW
authors.lastname: Ieong
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Johansson
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden ehrenberg@xray.bmc.uu.se.
authors.forename: Måns
authors.initials: M
authors.lastname: Ehrenberg
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001483:Base Sequence; D003062:Codon / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D003062:Codon; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; D006160:Guanosine Triphosphate
keywords: error hot spots; genetic code; kinetics; misreading; protein synthesis