Secretion of cell-wall glycoproteins by yeast protoplasts. Effect of 2-deoxy-d-glucose and cycloheximide
TL;DR: Results clearly show that blocking the synthesis of either part of the mannan-protein complex prevents the extracellular appearance of the other component.
Abstract: The effect of 2-deoxy-d-glucose and cycloheximide on the synthesis and secretion of the cell-wall constituents protein and mannan in yeast protoplasts was examined in detail. Although the 2-deoxy-d-glucose hardly influenced protein synthesis, a significant parallel inhibition of carbohydrate and protein secretion into the medium was observed. The mechanism of this inhibition is considered as an interference of metabolites of 2-deoxy-d-glucose with the synthesis of yeast mannan. Cycloheximide, which is an effective inhibitor of protein synthesis in yeast (Kerridge, 1958), inhibited the secretion of non-diffusible carbohydrate in yeast protoplasts, but on the other hand had no effect on the activity of particulate yeast mannan synthetase. Our results clearly show that blocking the synthesis of either part of the mannan–protein complex prevents the extracellular appearance of the other component. The nature of this phenomenon is discussed.
Citations
More filters
TL;DR: The chapter discusses the detailed structures of specific yeast mannans, and investigates the enzymic processes involved in mannan synthesis, using cell-free extracts and following incorporation of radioactive mannose into endogenous and exogenous acceptors.
Abstract: Publisher Summary The chapter focuses on the new developments concerning yeast mannan structure and biosynthesis as they relate to the organization of the cell wall and the roles played by these glycoproteins. The mechanism of mannan biosynthesis is still in a rudimentary state, partly because of the insufficient knowledge concerning mannan structure and partly because of the inherent difficulties in working with such a complex macromolecule. Detailed information of Saccharomyces cerevisiae mannan can now be sketched and facilitates the planning of experiments on, and the interpretation of results from, biosynthetic studies. Moreover, the availability of mannan mutants with known polysaccharide structural alterations should prove advantageous. Studies of mannan biosynthesis have taken three general tacks. One approach has been directed toward an elucidation of the overall process of mannan formation and translocation within the cell using “pulsechase” techniques and autoradiography. The second approach has dealt with the formation and secretion of intact mannan molecules by yeast protoplasts and the inhibition of this process by compounds that prevent protein or polysaccharide synthesis. The third approach has investigations of the enzymic processes involved in mannan synthesis, using cell-free extracts and following incorporation of radioactive mannose into endogenous and exogenous acceptors. The chapter discusses the detailed structures of specific yeast mannans.
314 citations
01 Jan 1980
TL;DR: As discussed in Chapter 1, one of the major classes of glycoproteins is that in which the carbohydrate chain is linked to the polypeptide chain by means of an N-glycosidic bond.
Abstract: As discussed in Chapter 1, one of the major classes of glycoproteins is that in which the carbohydrate chain is linked to the polypeptide chain by means of an N-glycosidic bond. As shown in Figure 1, this N-glycosidic bond is between an N-acetylglucosaminyl residue and the amido nitrogen of an asparagine residue in the polypeptide chain.
256 citations
TL;DR: A large number of the Wall Components studied had polysaccharide-protein complexes, and the structure of these complexes was similar to that of a cell wall, suggesting that wall architecture and structure-based determinants of wall growth and stability are similar.
206 citations
Cites background from "Secretion of cell-wall glycoprotein..."
...Impediment of mannosylation by 2-deoxyglucose in the presence of glucose or fructose as respective carbon sources (80, 139, 141, 162, 261) or by tunicamycin (142, 143) results in inhibition of the formation and secretion of the exocellular mannoprotein enzymes invertase and acid phosphatase....
[...]
...Cycloheximide does not affect the activity of the isolated mannan-synthesizing enzyme system (80, 232); neither does it influence the relatively low turnover of the corresponding enzymes (75)....
[...]
...When the formation of proteins is blocked by cycloheximide in intact cells (74) or protoplasts (80, 162, 256, 261), the formation and extracellular appearance of mannoproteins and mannoprotein enzymes are halted after a short delay....
[...]
TL;DR: The results demonstrate that differences in biological activity can be discriminated among tunicamycin homologs.
187 citations
TL;DR: The carbohydrate moieties of rat liver transferrin or apoprotein B of chick liver VLDL do not appear to play an essential role in the secretion process, and despite the inhibitory effect of tunicamycin on glycosylation, secretion of all four proteins was virtually unimpaired.
177 citations