Yeasts cell membranes

Catechins Yeasts Cell membrane Polyenes Stimulation membrane permeability increased intracellular catechin concentration [53]... 

A wide range of mammalian proteins have been expressed in S. pombe. In a successful example, the human lipocortin I comprised 50% of the total soluble proteins in yeast cells and showed high activity, indicating that the post-translational modifications were mammalian-like [104]. Membrane proteins including cytochrome P450 were expressed at ten times the levels of those in other yeast systems [105]. Also, GPCRs have been expressed in S. pombe, where the human dopamine D2 receptor was correctly inserted into the yeast cell membrane and demonstrated expression levels three times those of S. cerevisiae [106]. 

Azoles are synthetic antimycotic agents that act by inhibiting replication of yeast cells through interfering with the synthesis of ergosterol, the main sterol in the yeast cell membrane. 

Steveninck, J. V. Ledeboer, A. M. (1974). Phase transitions in the yeast cell membrane—the influence of temperature on the reconstitution of active dry yeast. Biochim. Biophys. Acta 352,64-70. 

It is used principally in the treatment of tinea pedis, tinea cruris, tinea corporis, tinea manuum, and tinea versicolor. Haloprogin s mechanisms of action in yeast cells are thought to be inhibition of respiration and disruption of yeast cell membranes. Its mechanism of action in dermatophytes is unknown. 

The yeast cell membrane may be envisioned as a selectively permeable barrier that serves a vital role in the organism s ability to maintain osmotic balance and regulate transport of essential nutrients into and metabolites (including ethanol) out of the cell. Ethanol is soluble in both aqueous and lipid phases of the cell membrane and its formation and passive effusion eventually interferes with structure and function of the membrane. Particularly important in this regard are the cell-membrane-associated transport enzymes such as those responsible for uptake of sugars and critical amino acids. During active fermentation at warm temperatures, ethanol accumulates intracellularly faster than it can be eliminated from the cell. This situation worsens as extracellular concentrations increase. Thus, temperature- and ethanol-directed inhibition is likely the result of the time delay arising from passive diffusion coupled with impaired membrane function. 

The primary antimicrobial form of SO2 is molecular or unionised SO2, followed by bisulphite and sulphite forms, which have minimal antimicrobial activity (Ough et al, 1983). The undissociated, molecular form penetrates the yeast cell membrane by diffusion and subsequently inactivates intracellular constituents (Schmiz, 1980 Stratford and Rose, 1986). In the cell, SO2 activates ATPase (adenosine triphosphatase), the ATP-hydrolysing enzyme, causing a decrease in the concentration of ATP furthermore, once the SO2 has entered the yeast cell, it dissociates, in response to the difference between the pH of grape juice and that of the cell, and becomes trapped. The bisulphite and sulphite ions then react with the cellular constituents. The combined effects of ATP depletion and cellular activity lead to inactivation and eventual death of the cell (Schmiz and Holzer, 1977 Beech and Thomas, 1985 Stratford and Rose, 1986). 

Because enzymes can be intraceUularly associated with cell membranes, whole microbial cells, viable or nonviable, can be used to exploit the activity of one or more types of enzyme and cofactor regeneration, eg, alcohol production from sugar with yeast cells. Viable cells may be further stabilized by entrapment in aqueous gel beads or attached to the surface of spherical particles. Otherwise cells are usually homogenized and cross-linked with glutaraldehyde [111-30-8] to form an insoluble yet penetrable matrix. This is the method upon which the principal industrial appHcations of immobilized enzymes is based. 

In terms of evolutionary biology, the complex mitotic process of higher animals and plants has evolved through a progression of steps from simple prokaryotic fission sequences. In prokaryotic cells, the two copies of replicated chromosomes become attached to specialized regions of the cell membrane and are separated by the slow intrusion of the membrane between them. In many primitive eukaryotes, the nuclear membrane participates in a similar process and remains intact the spindle microtubules are extranuclear but may indent the nuclear membrane to form parallel channels. In yeasts and diatoms, the nuclear membrane also remains intact, an intranuclear polar spindle forms and attaches at each pole to the nuclear envelope, and a single kinetochore microtubule moves each chromosome to a pole. In the cells of higher animals and plants, the mitotic spindle starts to form outside of the nucleus, the nuclear envelope breaks down, and the spindle microtubules are captured by chromosomes (Kubai, 1975 Heath, 1980 Alberts et al., 1989). 

In Saccharomyces cerevisiae, as in most eukaryotic cells, the plasma membrane is not freely permeable to nitrogenous compounds such as amino acids. Therefore, the first step in their utilization is their catalyzed transport across the plasma membrane. Most of the transported amino acids are accumulated inside the yeast cells against a concentration gradient. When amino acids are to be used as a general source of nitrogen, this concentration is crucial because most enzymes which catalyze the first step of catabolic pathways have a low affinity for their substrates. 

Schneiter, R. Brugger, B. Sandhoff, R. Zellnig, G. Leber, A. Lampl, M. Athenstaedt, K. Hrastnik, C. Eder, S. Daum, G. Paltauf, F. Wieland, F. T. Kohlwein, S. D. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of the lipid molecular species composition of yeast subcellular membranes reveals acyl chain-based sorting/remodeling of distinct molecular species en route to the plasma membrane. J. Cell Biol. 1999,146,741-754. 

Figure 12.2 Copper chaperone function, (a) Copper homeostasis in Enterococcus hirae is affected by the proteins encoded by the cop operon. CopA, Cu1+-import ATPase CopB, Cu1+-export ATPase CopY, Cu1+-responsive repressor copZ, chaperone for Cu1+ delivery to CopY. (b) The CTR family of proteins transports copper into yeast cells. Atxlp delivers copper to the CPx-type ATPases located in the post Golgi apparatus for the maturation of Fet3p. (c) Coxl7p delivers copper to the mitochondrial intermembrane space for incorporation into cytochrome c oxidase (CCO). (d) hCTR, a human homologue of CTR, mediates copper-ion uptake into human cells. CCS delivers copper to cytoplasmic Cu/Zn superoxide dismutase (SOD1). Abbreviations IMM, inner mitochondrial membrane OMM, outer mitochondrial membrane PM, plasma membrane PGV, post Golgi vessel. Reprinted from Harrison et al., 2000. Copyright (2000), with permission from Elsevier Science.

Arndt and Ahlers [38] used X-ray powder diffraction method for studying the influence of cations on the mode of action of miconazole on yeast cells. The influence of miconazole nitrate on yeast plasma membranes was studied in a concentration range of 0-100 pM. The reaction of 100 pM miconazole with the... 

Seaman, M., McCaffery, J., and Emr, S. (1998). A membrane coat complex essential for endosome-to-Golgi retrograde transport in yeast./. Cell Biol. 142, 665-681. 

R. Deubiquitination step in the endocytic pathway of yeast plasma membrane proteins crucial role of Doa4p ubiquitin isopeptidase, Mol Cell Biol, 2001, 21, 4482-94. 

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