title: Comparison of the complete sequence of the str operon in Salmonella typhimurium and Escherichia coli.
abstract: The nucleotide (nt) sequences of the str operon in Escherichia coli K-12 and Salmonella typhimurium LT2 were completed and compared at the nt and amino acid (aa) level. The order of conservation at the nt and aa level is rpsL greater than tufA greater than rpsG greater than f usA. A striking difference is that the rpsG-encoded ribosomal protein, S7, in E. coli K-12 is 23 aa longer than in S. typhimurium. The very low (0.18) codon adaptation index of this part of the E. coli K-12-encoding gene and the unusual stop codon (UGA) suggest that this is a relatively recent extension. A trend towards a higher G+C content in fusA (gene encoding elongation factor (EF)-G) and tufA (gene encoding EF-Tu) in S. typhimurium is noted. In fusA, nt substitutions at all three positions in a codon occur at a much higher frequency than expected from the number of nt substitutions in the gene, assuming they are random and independent events. An analysis of substitutions in this and other genes suggests that the triple substitutions in fusA, and some other genes, are the result of the sequential accumulation of individual mutations, probably driven by selection pressure for particular codons or aa.
authors.affiliation: Department of Molecular Biology, Uppsala University, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Johanson
authors.forename: D
authors.initials: D
authors.lastname: Hughes
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D020653:Peptide Elongation Factor G; D010444:Peptide Elongation Factor Tu / Q000235:genetics; D010445:Peptide Elongation Factors / Q000235:genetics; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins / Q000235:genetics*; D012486:Salmonella typhimurium / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins; C000717190:RpsI protein, E coli; C034212:ribosomal protein S12; C037442:ribosomal protein S7; D010444:Peptide Elongation Factor Tu