Cloning and characterization of ERG25, the Saccharomyces cerevisiae gene encoding C-4 sterol methyl oxidase.
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.
Bard
M
M
Department of Biology, Indiana University-Purdue University at Indianapolis, IN 46202, USA.
Bruner
D A
DA
Pierson
C A
CA
Lees
N D
ND
Biermann
B
B
Frye
L
L
Koegel
C
C
Barbuch
R
R
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
D006899:Mixed Function Oxygenases; C027532:methylsterol monooxygenase