title: Phylogeny of metabolic pathways: O-acetylserine sulphydrylase A is homologous to the tryptophan synthase beta subunit.
abstract: The cysK gene of Escherichia coli K-12 encoding O-acetylserine sulphydrylase A, was cloned and its nucleotide sequence, together with that of the flanking regions, was determined. The deduced amino acid sequence of the carboxy-terminal moiety of O-acetylserine sulphydrylase A shows significant similarity to the amino acid sequence of tryptophan synthase beta chain from several organisms. This sequence similarity is likely to reflect the structural homologies of substrates shared by both enzymes. This may indicate that these proteins, although catalysing different reactions in different metabolic pathways, have evolved from a common ancestral gene.
authors.affiliation: Unité de Régulation de l'Expression Génétique, Institut Pasteur, Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Levy
authors.forename: A
authors.initials: A
authors.lastname: Danchin
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D003547:Cysteine Synthase / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial; D008190:Lyases / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011732:Pyridoxal Phosphate / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014367:Tryptophan Synthase / Q000235:genetics*
chemical_list: D011732:Pyridoxal Phosphate; D003547:Cysteine Synthase; D008190:Lyases; D014367:Tryptophan Synthase