title: The complete nucleotide sequence of the ilvGMEDA cluster of Escherichia coli K-12.
abstract: The ilvGMEDA gene cluster of Escherichia coli K-12 has been the focus of intensive genetic and biochemical analysis for the past 30 years. Genetic regulation of the ilvGMEDA cluster involves attenuation, internal promoters, internal Rho-dependent termination sites, a site of polarity in the ilvG pseudogene of the wild-type organism, and autoregulation by the ilvA gene product, the biosynthetic L-threonine deaminase. We have now completed the nucleotide sequence of the 6600-bp cluster and have analyzed it, along with the ilvYC, ilvBN, and ilvIH genes, for codon frequencies and possible evolutionary relationships. The isoleucine content of each of the gene products of the ilvGMEDA cluster is quite similar (less than a two-fold variation), thus excluding one possible interpretation of the isoleucine-specific downstream amplification phenomenon. There is no evidence for retrograde evolution in the cluster since no significant homologies are detectable among genes that catalyze sequential reactions of the pathway. A highly significant homology does exist, however, between the threonine deaminases of yeast mitochondria and E. coli. The sequence at the boundary of the ilvA and ilvD genes is TAATAATG, so that the second TAA stop codon of ilvD overlaps the ATG initiation codon of ilvA.
authors.affiliation: Department of Microbiology, Mount Sinai School of Medicine, New York, NY 10029.
authors.forename: J L
authors.initials: JL
authors.lastname: Cox
authors.forename: B J
authors.initials: BJ
authors.lastname: Cox
authors.forename: V
authors.initials: V
authors.lastname: Fidanza
authors.forename: D H
authors.initials: DH
authors.lastname: Calhoun
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D005075:Biological Evolution; D003062:Codon / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D007256:Information Systems; D008969:Molecular Sequence Data; D005810:Multigene Family
chemical_list: D001426:Bacterial Proteins; D003062:Codon