title: Structure and regulation of cysD, the homocysteine synthase gene of Aspergillus nidulans.
abstract: The A. nidulans cysD gene encoding homocysteine synthase (O-acetyl-L-homoserine sulphydrylase) has been isolated by functional complementation of a cysD11 mutation. The gene contains five short introns and codes for a protein of 437 amino acids. The protein shows homology with bacterial and yeast O-acetyl- and O-succinyl-homoserine sulphydrylases, particularly from Schizosaccharomyces pombe, Saccharomyces cerevisiae and Kluyveromyces lactis. The cysD cDNA is able to complement a S. cerevisiae mutation impairing homocysteine synthase. Synthesis of the cysD mRNA is down-regulated by a high concentration of methionine in growth medium without sulphate and up-regulated under sulphur limitation. A comparison of cysD genomic and cDNA copies, derived from different A. nidulans strains, revealed a marked DNA-sequence polymorphism manifested mostly by silent point mutations. There was, however, much less polymorphism in the protein sequence.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawi'nskiego 5a, 02-106 Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Sieńko
authors.forename: J
authors.initials: J
authors.lastname: Topczewski
authors.forename: A
authors.initials: A
authors.lastname: Paszewski
mesh_terms: D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D019757:Carbon-Oxygen Lyases / Q000737:chemistry / Q000235:genetics*; D003001:Cloning, Molecular; D003547:Cysteine Synthase; D018076:DNA, Complementary / Q000302:isolation & purification; D004271:DNA, Fungal / Q000737:chemistry; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment
chemical_list: D018076:DNA, Complementary; D004271:DNA, Fungal; D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D003547:Cysteine Synthase; C103381:MET17 protein, S cerevisiae; C018725:O-acetylhomoserine (thiol)-lyase; D019757:Carbon-Oxygen Lyases