title: Nucleotide sequence, function, activation, and evolution of the cryptic asc operon of Escherichia coli K12.
abstract: The cryptic asc (previous called "SAC") operon of Escherichia coli K12 has been completely sequenced. It encodes a repressor (ascG); a PTS enzyme IIasc for the transport of arbutin, salicin, and cellobiose (ascF); and a phospho-beta-glucosidase that hydrolyzes the sugars which are phosphorylated during transport (ascB). ascG and ascFB are transcribed from divergent promoters. The cryptic operon is activated by the insertion of IS186 into the ascG (repressor) gene. The ascFB genes are paralogous to the cryptic bglFB genes, and ascG is paralogous to galR. The duplications that gave rise to these paralogous genes are estimated to have occurred approximately 320 Mya, a time that predates the divergence of E. coli and Salmonella typhimurium.
authors.affiliation: Biology Department, University of Rochester, New York 14627.
authors.forename: B G
authors.initials: BG
authors.lastname: Hall
authors.forename: L
authors.initials: L
authors.lastname: Xu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D005075:Biological Evolution; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics*; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial