1. Localization of synthesis of β1,6-glucan in Saccharomyces cerevisiae
- Author
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Montijn, R.C., Vink, E., Müller, W.H., Verkleij, A.J., Ende, H. van den, Henrissat, B., Klis, F.M., and Centraal Instituut voor Voedingsonderzoek TNO
- Subjects
beta-Glucans ,Saccharomyces cerevisiae Proteins ,Glycoside Hydrolases ,Protein Conformation ,Molecular Sequence Data ,Beta 1,6 glucan ,Transglycosidase enzyme system ,Membrane vesicle ,Chitin ,Saccharomyces cerevisiae ,Biosynthesis ,Cell surface ,Protein Structure, Secondary ,Amino acid sequence ,Fungal Proteins ,Synthesis ,Multienzyme Complexes ,Transferases ,Glucosyltransferase ,Saccharomyces cerevisiae protein ,Molecular genetics ,Glucans ,Nutrition ,Priority journal ,Fungal protein ,Cell wall ,KRE6 protein, S cerevisiae ,Cell Membrane ,Microsome ,Membrane Proteins ,Beta glucan ,Multienzyme complex ,Nonhuman ,Glucan ,Glycosidase ,Golgi complex ,Metabolism ,Membrane protein ,Protein secondary structure ,SKN1 protein, S cerevisiae ,Transferase ,Nucleotide sequence ,Endoplasmic reticulum ,Beta-1,6-glucan - Abstract
β1,6-Glucan is a key component of the yeast cell wall, interconnecting cell wall proteins, β1,3-glucan, and chitin. It has been postulated that the synthesis of β1,6-glucan begins in the endoplasmic reticulum with the formation of protein-bound primer structures and that these primer structures are extended in the Golgi complex by two putative glucosyltransferases that are functionally redundant, Kre6 and Skn1. This is followed by maturation steps at the cell surface and by coupling to other cell wall macromolecules. We have reinvestigated the role of Kre6 and Skn1 in the biogenesis of β1,6- glucan. Using hydrophobic cluster analysis, we found that Kre6 and Skn1 show significant similarities to family 16 glycoside hydrolases but not to nucleotide diphospho-sugar glycosyltransferases, indicating that they are glucosyl hydrolases or transglucosylases instead of genuine glucosyltransferases. Next, using immunogold labeling, we tried to visualize intracellular β1,6-glucan in cryofixed sec1-1 cells which had accumulated secretory vesicles at the restrictive temperature. No intracellular labeling was observed, but the cell surface was heavily labeled. Consistent with this, we could detect substantial amounts of β1,6-glucan in isolated plasma membrane-derived microsomes but not in post-Golgi secretory vesicles. Taken together, our data indicate that the synthesis of β1,6-glucan takes place largely at the cell surface. An alternative function for Kre6 and Skn1 is discussed.
- Published
- 1999