Yeasts cell wall

Manners D.J., Masson A.J. Patterson J.C. (1973a) The sductiwe of a j8-(l-3)-D-glucan fixMn yeast cell walls. BiochemJ, 135, 19-30. 

Figure 1.15. Complement activation via the alternative pathway. Always present in serum are trace amounts of C3b, which may attach to recognition sites on, for example, yeast cell walls. C3b may combine with serum factor B to form C3bB, and this complex is acted upon by factor D to form C3bBb. This latter complex is a C3 convertase and may act upon C3 to form more C3b to amplify the process. The C3bBb-coated particles may activate other complement components (C4-C9) or be recognised by complement receptors on neutrophils.

Domain present in yeast cell wall integrity and stress response component proteins Domain with 2 conserved Trp (W) residues f3/y crystallins A20-like zinc fingers ANl-like zinc finger... 

K. Miscellaneous Issues 1. Sorting of Yeast Cell Wall Proteins... 

When in later years Krebs reviewed the major points which had to be established if the cycle was to be shown to be operative in cells, the obvious needs were to find the presence of the required enzymes and to detect their substrates. As the substrates are present in the cycle in catalytic amounts their accumulation required the use of inhibitors. Krebs also stressed that rates of oxidation of the individual substrates must be at least as fast as the established rates of oxygen uptake in vivo, an argument first used by Slator (1907) with reference to fermentation A postulated intermediate must be fermented at least as rapidly as glucose is. (See Holmes, 1991). This requirement did not always appear to be met. In the early 1950s there were reports that acetate was oxidized by fresh yeast appreciably more slowly than the overall rate of yeast respiration. It was soon observed that if acetone-dried or freeze-dried yeasts were used in place of fresh yeast, rates of acetate oxidation were increased more than enough to meet the criterion. Acetate could not penetrate fresh yeast cell walls sufficiently rapidly to maintain maximum rates of respiration. If the cell walls were disrupted by drying this limitation was overcome, i.e. if rates of reaction are to be... 

Synergism between l,3-/9-Glucanases in Yeast Cell Wall Zymolysis... 

The lytic enzyme systems, active against yeast cell walls, usually contain l,3-/ -glucanases, proteases, mannanases, chitinases, and 1,6-) -glucanases. The proportion of those enzyme activities, their action pattern, synergism, and dependence on inhibitors constitute the activity profile... 

BIELECKI AND GALAS Yeast Cell Wall Zymolysis 477... 

In some cases, microbial cell fragments may arise and can be particularly problematic. For example, the disc centrifuges often used to remove yeast after brewery fermentations are known to produce shearing forces that break off yeast cell wall fragments (Siebert et ah, 1987). Agitation of yeast by other means is also problematic (Lewis and Poerwantaro, 1991 Stoupis et ah, 2003). In beer, the resulting particles resist sedimentation and impair filtration. 

A fluorescent tag (fluorescein isothiocyanate) attached to the lectin Concanavalin A is useful in staining yeast cell wall fragments (Siebert et al., 1981). Concanavalin A specifically binds to mannan, which is prominent in yeast cell walls. 

Fig. 2.—Diagram of Hypothetical Structure of Yeast Cell-wall JPhosphoric diester links are represented by —P— (E) is 0-D-fructofuranosidase is D-glucan is D-mannan and S is sulfur. From Ref. 117 printed here by permission of Cambridge University Press.]...

Following a stimulation by the yeast cell wall extract zymosan, phagocytosing human leukocytes show an enhanced oxygen consumption, the cyanide-insensitive respiratory burst , after a lag period of 30-40 s. The production of superoxide anions, measured by the reduction of Fe(ni)-cytochrome c, followed the same... 

Of the particulate stimuli certain ones are far more active when they are coated with proteins from serum (opsonized) than when they are not. However, others like latex beads elicit formation of Oj" by PMNs without opsonization DeChatelet et al. found that the production of O by PMNs from man and rabbit was stimulated by opsonized but not unopsonized zymosan (fragments of yeast cell walls). Bacteria alone were found to stimulate the formation of O but in the presence of serum bacteria stimulated the formation of O7 three fold However, the stimulatory effect of bacteria appeared to be caused by changes which the bacteria produced by an interaction with constitutents of serum, because serum itself after exposure to the bacteria stimulated production of O by PMNs. The active component from serum was heat sensitive (100°) and not sedimentable at 105,000 g. Whether this material was derived from the components of serum or from the bacteria is not clear but may have been a protein of the complement system. 

Mannoprotein of yeast cell walls 185 Mannose (Man) 161s, 163s Mannose-6-phosphate 185 Mannose-6-phosphate isomerase 693 MAP kinase cascade 576-578 figure 579... 

Transfection, DNA uptake in eukaryotic systems, often is more problematic then bacterial transformation the mode of DNA uptake is poorly understood and efficiency is much lower. In yeast, cell walls can be digested with degradative enzymes to yield fragile protoplasts, which are then able to take up DNA. Cell walls are resynthesized after removal of the degrading enzymes. Mammalian cells take up DNA after precipitation onto their surface with calcium phosphate [Fugene 6 (Roche) Lipofectin (Life Technologies) Effectene (Qiagen)]. Electroporation is often more efficient for transfection in eukaryotic cell systems, especially in yeasts. 

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