Synthesis of monohydroxylated inositolphosphorylceramide (IPC-C) in Saccharomyces cerevisiae requires Scs7p, a protein with both a cytochrome b5-like domain and a hydroxylase/desaturase domain.
Saccharomyces cerevisiae mutants lacking Scs7p fail to accumulate the inositolphosphorylceramide (IPC) species. IPC-C, which is the predominant form found in wild-type cells. Instead scs7 mutants accumulate an IPC-B species believed to be unhydroxylated on the amide-linked C26-fatty acid. Elimination of the SCS7 gene suppresses the Ca(2+)-sensitive phenotype of csg1 and csg2 mutants. The CSG1 and CSG2 genes are required for mannosylation of IPC-C and accumulation of IPC-C by the csg mutants renders them Ca(2+)-sensitive. The SCS7 gene encodes a protein that contains both a cytochrome b5-like domain and a domain that resembles the family of cytochrome b5-dependent enzymes that use iron and oxygen to catalyse desaturation or hydroxylation of fatty acids and sterols. Scs7p is therefore likely to be the enzyme that hydroxylates the C26-fatty acid of IPC-C.
Dunn
T M
TM
Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
Haak
D
D
Monaghan
E
E
Beeler
T J
TJ
D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003573:Cytochrome b Group / Q000737:chemistry*; D005800:Genes, Fungal; D006900:Hydroxylation; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D016366:Open Reading Frames; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids / Q000096:biosynthesis*
C086192:CSG2 protein, S cerevisiae; D002135:Calcium-Binding Proteins; D003573:Cytochrome b Group; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; D006899:Mixed Function Oxygenases; C109314:Scs7 protein, S cerevisiae; D002118:Calcium