Hut1 proteins identified in Saccharomyces cerevisiae and Schizosaccharomyces pombe are functional homologues involved in the protein-folding process at the endoplasmic reticulum.
The Saccharomyces cerevisiae HUT1 gene (scHUT1) and the Schizosaccharomyces pombe hut1(+) gene (sphut1(+)) encode hydrophobic proteins with approximately 30% identity to a human UDP-galactose transporter-related gene (UGTrel1) product. These proteins show a significant similarity to the nucleotide sugar transporter and are conserved in many eukaryotic species, but their physiological functions are not known. Both scHUT1 and sphut1(+) genes are non-essential for cell growth under normal conditions, and their disruptants show no defects in the modification of O- and N-linked oligosaccharides, but are sensitive to a membrane-permeable reducing agent, dithiothreitol (DTT). Consistent with this phenotype, scHUT1 has genetic interaction with ERO1, which plays an essential role in the oxidation of secretory proteins at the endoplasmic reticulum (ER). Overexpression of the MPD1 or MPD2 genes, which were isolated as multicopy suppressors of protein disulphide isomerase (PDI) depletion, could not replace the essential function of PDI in Delta hut1 S. cerevisiae cells. Our results indicate that scHut1p and spHut1p are functional homologues, and their physiological function is to maintain the optimal environment for the folding of secretory pathway proteins in the ER.
Nakanishi
H
H
Department of Applied Biological Science, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan.
Nakayama
K
K
Yokota
A
A
Tachikawa
H
H
Takahashi
N
N
Jigami
Y
Y
D000595:Amino Acid Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D004271:DNA, Fungal / Q000235:genetics; D004229:Dithiothreitol / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D005656:Fungal Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D006023:Glycoproteins / Q000235:genetics / Q000502:physiology; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D033704:Nucleotide Transport Proteins; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D019704:Protein Disulfide-Isomerases / Q000235:genetics / Q000502:physiology; D017510:Protein Folding; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013499:Surface Properties
D004271:DNA, Fungal; D005656:Fungal Proteins; D006023:Glycoproteins; C433884:HUT1 protein, S cerevisiae; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D033704:Nucleotide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; C405327:ERO1A protein, human; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; C113186:ERO1 protein, S cerevisiae; D019704:Protein Disulfide-Isomerases; D004229:Dithiothreitol