title: The purB gene of Escherichia coli K-12 is located in an operon.
abstract: The structural gene (purB) for succinyl-AMP (S-AMP) lyase and three additional ORFs are on the same DNA strand of the chromosome of Escherichia coli. Cassette mutagenesis and primer extension mapping demonstrated that purB is co-transcribed with an upstream gene (ORF23, or ycfC) encoding a 22.9 kDa membrane-associated protein of non-essential, but unknown, function unrelated to purine biosynthesis. The purB operon lies between phoP and an ORF expressing an essential function which may correspond to asuE (trmU). S-AMP lyase was purified to near homogeneity. The purified enzyme is a homotetramer of 50 kDa subunits, has a K(m) for S-AMP of 3.7 microM and a pH optimum of 7.4-7.6.
authors.affiliation: Department of Biochemistry, University of Southampton, Crescent East, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Green
authors.forename: T
authors.initials: T
authors.lastname: Malik
authors.forename: I G
authors.initials: IG
authors.lastname: Giles
authors.forename: W T
authors.initials: WT
authors.lastname: Drabble
mesh_terms: D000264:Adenylosuccinate Lyase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D002876:Chromosomes, Bacterial / Q000235:genetics; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D016366:Open Reading Frames; D009876:Operon; D011487:Protein Conformation; D015183:Restriction Mapping; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D000264:Adenylosuccinate Lyase