title: Unusual codon bias occurring within insertion sequences in Escherichia coli.
abstract: The large open reading frames of insertion sequences from Escherichia coli were examined for their spatial pattern of codon usage bias and distribution of rarely used codons. There is a bias in codon usage that is generally lower toward the terminal ends of the coding regions, which is reflected in the occurrence of an excess of nonpreferred codons in the 3' portions of the coding regions as compared with the 5' portions. In contrast, typical chromosomal genes have a lower codon usage bias toward the 5' ends of the coding regions. These results imply that the selective forces reflected in codon usage bias may differ according to position within the coding sequence. In addition, these constraints apparently differ in important ways between genes contained in insertion sequences and those in the chromosome.
authors.affiliation: Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110.
authors.forename: J G
authors.initials: JG
authors.lastname: Lawrence
authors.forename: D L
authors.initials: DL
authors.lastname: Hartl
mesh_terms: D002876:Chromosomes, Bacterial / Q000502:physiology; D003062:Codon / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D016366:Open Reading Frames / Q000235:genetics; D012641:Selection, Genetic
chemical_list: D003062:Codon; D004251:DNA Transposable Elements