Cytoplasm of yeast

Nonsense-mediated decay occurs in the cytoplasm of yeast cells. Remarkably, In mammalian cells, there Is evi-... 

Intracellular transport of metal ions has been a very well studied research area in the last few years. The most often-cited case of this transport involves copper transport in yeast by the copper metallochaperones 24, 25). Cu(I) enters the cytoplasm of yeast via copper transport receptors, and Cu(I) is bound by one of three transport proteins Lys7, Atxl, or Cox 17. Lys7 delivers copper to CuZn superoxide dismutase, Atxl delivers copper to ccc2 that activates an Fe(II) uptake system, and Cox 17 delivers copper to the mitochondria for the ultimate uptake into cytochrome c oxidase. A similar copper transport system has been reported in humans (26), and there may be a system in bacteria as well (27). Metal ion transport systems are known for iron, nickel, and manganese 24, 25, 28). However, no cytoplasmic Zn(II) transporters have been identified in... 

In an ideal stain, the cytoplasm of cysts and trophozoites is blue-green tinged with purple. Entamoeba coli cyst cytoplasm is often more purple than that of other species. Nuclear chromatin, chromatoid bodies, erythrocytes, and bacteria stain red or purplish red. Other ingested particles such as yeasts often stain green. Parasite eggs and larvae usually stain red. Inflammatory cells and tissue cells stain in a fashion similar to that of protozoa. Color reactions may vary from the above. 

The distribution of elements in single-cell non-photosynthetic eukaryotes is probably best seen in terms of the well-defined compartments of yeast. The central cytoplasmic compartment containing the nucleus has many free element concentrations, only somewhat different from those in all known aerobic prokaryotes (Figure 7.7). (The nuclear membrane is a poor barrier to small molecules and ions and so we include the nucleus with the cytoplasm.) We do not believe in fact that the free cytoplasmic values of Mg2+, Mn2+, Fe2+, Ca2+, and possibly Zn2+, have changed greatly throughout evolution. As stressed already there are limitations since free Mg2+ and Fe2+ are essential for the maintenance of the primary synthetic routes of all cells, and changes in other free metal ions could well have imposed... 

Atkin AL, Altamura N, Leeds P, Culbertson MR (1995) The majority of yeast UPFl co-localizes with polyribosomes in the cytoplasm. Mol Biol Cell 6 611-625... 

Other ATP-dependent proton pumps are present in the plasma membranes of yeast and other fungi274b and also in the acid-secreting parietal cells of the stomach (Fig. 18-17). The H+-ATPase of Neurospora pumps H+ from the cytoplasm without a counterion. 

Not all hereditary traits follow the Mendelian patterns expected for chromosomal genes. Some are inherited directly from the maternal cell because their genes are carried in the cytoplasm rather than the nucleus. There are three known locations for cytoplasmic genes the mitochondria, the chloroplasts, and certain other membrane-associated sites.285 286 An example of the last is found in "killer" strains of yeast. Cells with the killer trait release a toxin that kills sensitive cells but are themselves immune. The genes are carried in double-stranded RNA rather than DNA, but are otherwise somewhat analogous to the colicin factors of enteric bacteria (Box 8-D). Similar particles (kfactors) are found in Paramecium.287... 

A number of different proteolytic systems are thought to be responsible for the degradation of soluble proteins in the cytoplasm of eukaryotic cells. One of the best understood is that which involves ATP and the protein ubiquitin. Ubiquitin is a small protein of only 76 residues. It occurs universally in eukaryotic cells and is highly conserved in sequence only three residues distinguish the ubiquitin in yeast and humans. The covalent attachment of ubiquitin to proteins is thought to tag them for subsequent hydrolysis by cellular proteases. 

The term nucleoside was originally proposed by Levene and Jacobs in 1909 for the carbohydrate derivatives of purines (and, later, of pyrimidines) isolated from the alkaline hydrolyzates of yeast nucleic acid. The phosphate esters of nucleosides are the nucleotides, which, in polymerized forms, constitute the nucleic acids of all cells.2 The sugar moieties of nucleosides derived from the nucleic acids have been shown, thus far, to be either D-ribose or 2-deoxy-D-eri/fAro-pentose ( 2-deoxy-D-ribose ). The ribo-nucleosides are constituents of ribonucleic acids, which occur mainly in the cell cytoplasm whereas 2-deoxyribo -nucleosides are components of deoxypentonucleic acids, which are localized in the cell nucleus.3 The nucleic acids are not limited (in occurrence) to cellular components. They have also been found to be important constituents of plant and animal viruses. 

The Fab fragment of 1F7 has already been shown to function in the cytoplasm of a chorismate mutase-deficient yeast strain [43,44]. When produced at a sufficiently high level, the catalytic antibody is able to replace the missing enzyme and weakly complement the metabolic defect. Conceivably, therefore, it can be placed under selection pressure to identify variants that have higher catalytic efficiency. Preliminary results from such experiments appear quite promising [69]. 

Several additional lines of evidence indicate that presequence function is governed by conformational properties of the precursor. The target peptide of yeast mitochondrial cytochrome oxidase subunit IV (COX), fused to murine dihydrofolate reductase (DHFR, a cytoplasmic enzyme). 

Fig. 3A.1 LTSEM images of yeast cells after 24 h of induced autolysis in a model wine system, a Superficial ultrastructure of a yeast cell. b,c Images of fractured empty yeast cells which have lost most of their cytoplasmic content during the autolysis (Maitfnez-Rodrfguez AJ, Polo MC, Carrascosa AV (2001) Int J Food Microbiol 71 45-51. Copyright (2001). Elsevier)...

However, a smaller amount of cytoplasmic contents were solubilized after 12 months of yeast aging in sparkling wines under autolysis in natural conditions (Fig. 3A.2). This shows that the autolysis conditions during aging of sparkling wines elaborated by the traditional method are not optimal and it may take several months or years before this is finished. 

Carrier-mediated movement of sugars across the plasmalemma of yeasts involves the combination of the sugar with a protein on one side of the plasmalemma, followed by release of the sugar into the cytoplasm on the other side. Such movement is described either as (t) facilitated diffusion, when the movement requires no metabolic energy, or (ii) active transport, which involves the expenditure of metabolic energy. Sugars entering yeast cells by active transport may be accumulated within the cells to a concentration many hundred times the external level. This subject has been reviewed by... 

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