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.
Mesh Terms:
Amino Acid Sequence, Calcium, Calcium-Binding Proteins, Chromosome Mapping, Cloning, Molecular, Cytochrome b Group, Genes, Fungal, Hydroxylation, Mixed Function Oxygenases, Mutation, Open Reading Frames, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sphingolipids
Yeast
Date: Mar. 15, 1998
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