title: Cloning and characterization of ERG25, the Saccharomyces cerevisiae gene encoding C-4 sterol methyl oxidase.
abstract: We have cloned the Saccharomyces cerevisiae C-4 sterol methyl oxidase ERG25 gene. The sterol methyl oxidase performs the first of three enzymic steps required to remove the two C-4 methyl groups leading to cholesterol (animal), ergosterol (fungal), and stigmasterol (plant) biosynthesis. An ergosterol auxotroph, erg25, which fails to demethylate and concomitantly accumulates 4,4-dimethylzy-mosterol, was isolated after mutagenesis. A complementing clone consisting of a 1.35-kb Dra I fragment encoded a 309-amino acid polypeptide (calculated molecular mass, 36.48 kDa). The amino acid sequence shows a C-terminal endoplasmic reticulum retrieval signal KKXX and three histidine-rich clusters found in eukaryotic membrane desaturases and in a bacterial alkane hydroxylase and xylene monooxygenase. The sterol profile of an ERG25 disruptant was consistent with the erg25 allele obtained by mutagenesis.
authors.affiliation: Department of Biology, Indiana University-Purdue University at Indianapolis, IN 46202, USA.
authors.forename: M
authors.initials: M
authors.lastname: Bard
authors.forename: D A
authors.initials: DA
authors.lastname: Bruner
authors.forename: C A
authors.initials: CA
authors.lastname: Pierson
authors.forename: N D
authors.initials: ND
authors.lastname: Lees
authors.forename: B
authors.initials: B
authors.lastname: Biermann
authors.forename: L
authors.initials: L
authors.lastname: Frye
authors.forename: C
authors.initials: C
authors.lastname: Koegel
authors.forename: R
authors.initials: R
authors.lastname: Barbuch
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D008401:Gas Chromatography-Mass Spectrometry; D005800:Genes, Fungal; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics
chemical_list: D006899:Mixed Function Oxygenases; C027532:methylsterol monooxygenase