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  • 1
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; Yeast mating ; Cell-cell recognition ; Sexual agglutination ; Agglutinins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sex-specific agglutinins from the cell surface of haploid cells of Saccharomyces cerevisiae (X2180, mta and mtα) were purified and analysed. The constitutive agglutinin from mta cells was extractable with 3 mM dithiothreitol. It was shown to be a glycoprotein (3% mannose) with an apparent Mr of 43,000 based on gel filtration, but in SDS-PAGE it behaved as a much smaller molecule (Mr between 18,000 and 26,000). About one in three amino acids was a hydroxyamino acid. Its biological activity was resistant to boiling for 1 h, but sensitive to pronase. Intact mtα cells retained their agglutinability in the presence of dithiothreitol but limited trypsinizing released a biologically active agglutinin fragment. It had an apparent Mr of 320,000 (gel filtration). When analysed by SDS-PAGE, a single diffuse band with an apparent Mr of 225,000 was observed. The protein was 94% (w/w) mannose with a trace of N-acetyl glucosamine. Its biological activity was almost completely lost after boiling for 1 h. Both agglutinins behaved as monovalent molecules and specifically inhibited the biological activity of both noninduced and pheromone-induced cells. Pheromone treatment of mta cells resulted in an apparent 32-fold increase in agglutinin activity at the cell surface, whereas pheromone treatment of mtα cells only doubled the apparent agglutinin activity.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 25 (1971), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cell wall preparations of Convolvulus callus were found to contain α-glucosidase activity, the bulk of which could be solubilized by solutions of high ionic strength. Callus tissue incubated in 0.5 M KC1 released α-glucosidase activity into the washing medium as distinct from tissue incubated in 1.0 M sorbitol. The wall-bound activity of KCl-treated tissue was found to be less than that of sorbitol-treated tissue, while the difference between both activities proved to be equal to the enzyme activity found in the washing medium of KCl-treated tissue. Since no trace of cell leakage was observed, it is concluded that α-glucosidase activity is located at the cell surface. The level of this surface-located enzyme was not affected by the presence of maltose in the nutrient medium.
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  • 3
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The wall-bound invertase activity increased 3.3-fold upon transfer of fragments of Convolvulus callus to fresh solid nutrient medium and 7.7-fold upon transfer to liquid nutrient medium. Addition of actinomycin D, cycloheximide or the amino acid analogue thienylalanine brought about a further stimulation of the invertase content of the cell walls. The rise of wall-bound invertase activity was not due to redistribution of invertase activity between cytoplasm and cell walls, and appeared to be dependent on metabolic energy.An equation is presented to calculate the half-life of enzymes from their time-course. Applied on the time-courses of wall-bound invertase activity, a half-life of about 12 h was obtained in callus transferred to fresh solid medium and of about 5.4 h in tissue transferred to liquid medium. It is argued that the increase of invertase content of the cell walls is due to an enhanced rate of invertase synthesis.
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Low environmental pH strongly affected the organization of the Saccharomyces cerevisiae cell wall, resulting in rapidly induced resistance to β1,3-glucanase. At a molecular level, we found that a considerable amount of Cwp1p became anchored through a novel type of linkage for glycosylphosphatidylinositol (GPI)-dependent cell wall proteins, namely an alkali-labile linkage to β1,3-glucan. This novel type of modification for Cwp1p did not require the presence of a GPI-derived structure connecting the protein with β1,6-glucan. In addition, we found high levels of Cwp1p, which was double-anchored through both the novel alkali-sensitive bond to β1,3-glucan and the alkali-resistant GPI-derived linkage to β1,6-glucan. Further cell wall analyses demonstrated that Pir2p/Hsp150 and possibly other Pir cell wall proteins, which were already known to be linked to the β1,3-glucan framework by an alkali-sensitive linkage, were also more efficiently retained in the cell wall at pH 3.5 than at pH 5.5. Consequently, the alkali-sensitive type of linkage of cell wall proteins to β1,3-glucan was induced by low pH. The low pH-induced alterations in yeast cell wall architecture were demonstrated to be dependent on a functional HOG1 gene, but not on the Slt2p-mediated MAP kinase pathway. Consistent with this observation, DNA microarray studies revealed transcriptional induction of many known high-osmolarity glycerol (HOG) pathway-dependent genes, including four cell wall-related genes, namely CWP1, HOR7, SPI1 and YGP1.
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  • 5
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The growth rate of Convolvulus callus on a sucrose-containing medium appeared to be largely independent of the activity of cell wall invertase. The increase of this enzyme activity which occurs upon subculturing was unaffected within the first 24 h by the presence of the substrate sucrose. Neither substitution by glucose or fructose, nor complete deletion of the carbon source had any effect.Gibberellins apparently were not involved in the initiation and/or control of the increase of wall-bound invertase activity occurring upon subculturing. Exogenous ethylene was unable to mimick this effect of subculturing but when applied immediately after subculturing it had a synergistic effect on the increase of invertase. Inhibition occurred, however, when exposure to ethylene was delayed until after 24 h of incubation. These findings suggest a role of ethylene in the control of wall-bound invertase activity.
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The cell wall of yeast contains a major structural unit, consisting of a cell wall protein (CWP) attached via a glycosylphosphatidylinositol (GPI)-derived structure to β1,6-glucan, which is linked in turn to β1,3-glucan. When isolated cell walls were digested with β1,6-glucanase, 16% of all CWPs remained insoluble, suggesting an alternative linkage between CWPs and structural cell wall components that does not involve β1,6-glucan. The β1,6-glucanase-resistant protein fraction contained the recently identified GPI-lacking, O-glycosylated Pir-CWPs, including Pir2p/Hsp150. Evidence is presented that Pir2p/Hsp150 is attached to β1,3-glucan through an alkali-sensitive linkage, without β1,6-glucan as an interconnecting moiety. In β1,6-glucan-deficient mutants, the β1,6-glucanase-resistant protein fraction increased from 16% to over 80%. This was accompanied by increased incorporation of Pir2p/Hsp150. It is argued that this is part of a more general compensatory mechanism in response to cell wall weakening caused by low levels of β1,6-glucan.
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In Candida albicans wild-type cells, the β1,6-glucanase-extractable glycosylphosphatidylinositol (GPI)-dependent cell wall proteins (CWPs) account for about 88% of all covalently linked CWPs. Approximately 90% of these GPI-CWPs, including Als1p and Als3p, are attached via β1,6-glucan to β1,3-glucan. The remaining GPI-CWPs are linked through β1,6-glucan to chitin. The β1,6-glucanase-resistant protein fraction is small and consists of Pir-related CWPs, which are attached to β1,3-glucan through an alkali-labile linkage. Immunogold labelling and Western analysis, using an antiserum directed against Saccharomyces cerevisiae Pir2p/Hsp150, point to the localization of at least two differentially expressed Pir2 homologues in the cell wall of C. albicans. In mnn9Δ and pmt1Δ mutant strains, which are defective in N- and O-glycosylation of proteins respectively, we observed enhanced chitin levels together with an increased coupling of GPI-CWPs through β1,6-glucan to chitin. In these cells, the level of Pir-CWPs was slightly upregulated. A slightly increased incorporation of Pir proteins was also observed in a β1,6-glucan-deficient hemizygous kre6Δ mutant. Taken together, these observations show that C. albicans follows the same basic rules as S. cerevisiae in constructing a cell wall and indicate that a cell wall salvage mechanism is activated when Candida cells are confronted with cell wall weakening.
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  • 8
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glucose-limited bean cells (Phaseolus vulgaris L.) were grown in a modified bacterial fermentor at a constant pH of 4.8. The cultures were kept in steady state at different specific growth rates varying from 0.00216 h−1 to 0.0106 h−1. Culture conditions are described that are needed to start a continuous culture. First, it was essential to use log-phase cells as starting material. Second, it was important to increase the dilution rate gradually, otherwise cells in the culture aggregated. Cells grown at the highest dilution rate employed contained twice as much protein per gram dry weight as cells grown at the lowest dilution rate. The composition of the cell walls also varied with the dilution rate in contrast to their relatively constant composition when grown in batch culture.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Planta 144 (1979), S. 479-484 
    ISSN: 1432-2048
    Keywords: Cell suspension culture ; Cell wall ; Extension ; Hydroxyproline ; Phaseolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The arabinosylation patterns of wall-bound hydroxyproline in Phaseolus vulgaris L. cell suspension cultures were determined by separating free hydroxyproline and hydroxyproline-arabinose oligomers over a Bio-Gel P-2 column. Total hydroxyproline accounted for about 3.3% of wall dry weight during all growth phases of batch-cultured bean cells. The chemical arabinosylation patterns of wall-bound hydroxyproline varied during the lag phase and early log phase of the culture. First, an increase in nonglycosylated hydroxyproline occurred accompanied by a corresponding decrease in hydroxyproline tetra-arabinoside. During the early log phase the reverse happened. In later stages of growth the chemical arabinosylation patterns remained constant. The radiochemical arabinosylation patterns were also determined, after pulselabeling the cultures with [14C]proline at various times during growth, to be able to distinguish recently incorporated hydroxyproline. The time course of the arabinosylation pattern of this fraction indicated that the initial changes in the chemical pattern were due to the temporary incorporation of less extensively glycosylated hydroxyproline-containing protein into the cell wall.
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  • 10
    ISSN: 1432-2048
    Keywords: Cell elongation ; Cell wall ; Glucan ; Phaseolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hypocotyls of dark-grown 6-day-old seedlings of Phaseolus vulgaris L. proved to be sufficiently homogeneous to permit studies relating the rate of cell elongation to the composition of the primary cell walls. Whereas the levels of cellulose and uronic acids remained practically constant during and after cell extension, all other components showed major or minor changes. Cell-wall protein, as such, decreased by more than 50%, but indications are that hydroxyproline-rich glycoprotein increased with a decreasing rate of cell elongation, concomitant with a rise in the degree of arabinosylation of wall-bound hydroxyproline. As cell elongation slowed down, non-cellulosic glucose accumulated, presumably in the form of a β-(1–4)glucan closely associated with cellulose. These findings confirm the notion that the primary cell wall is a highly dynamic structure.
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