Saccharomyces cerevisiae uptake

Regulation of copper uptake has been studied in most detail in the yeast Saccharomyces cerevisiae. Uptake of Cu + is similar to fhaf of Fe. The same plasma membrane reducfase system, consisting of proteins Frelp and Fre2p (encoded by genes FRE1 and FRET), acts to reduce both Fe + and These two... 

Wang et al.2 and Najafpour et al.3A worked with immobilised microbial cells of Nitrobacer agilis, Saccharomyces cerevisiae and Pseudomonas aeruginosa in gel beads, respectively. They found separately that the cells retained more than 90% of their activity after immobilisation by using specific oxygen uptake rate (SOUR) [mg 02g 1 (dry biomass) h 11 as the biomass activity indicator. Such differences in immobilised biomass and activity between free and immobilised biomass activities depend strongly on the particular characteristics of the microbial systems and their interaction with the support matrix. 

The accumulation of a number of amino acids from the external medium seems almost irreversible in Saccharomyces cerevisiae. The first detailed study of this phenomenon concerned histidine [13]. Histidine uptake by the specific histidine permease HlPl is an energy dependent process which accumulates free and intact... 

Five structural genes for amino acid uptake systems have been cloned in Saccharomyces cerevisiae by functional complementation, and their putative amino acid sequences deduced from the respective nucleotide sequences (Fig. 2). 

Feedback inhibition of amino acid transporters by amino acids synthesized by the cells might be responsible for the well known fact that blocking protein synthesis by cycloheximide in Saccharomyces cerevisiae inhibits the uptake of most amino acids [56]. Indeed, under these conditions, endogenous amino acids continue to accumulate. This situation, which precludes studying amino acid transport in yeast in the presence of inhibitors of protein synthesis, is very different from that observed in bacteria, where amino acid uptake is commonly measured in the presence of chloramphenicol in order to isolate the uptake process from further metabolism of accumulated substances. In yeast, when nitrogen starvation rather than cycloheximide is used to block protein synthesis, this leads to very high uptake activity. This fact supports the feedback inhibition interpretation of the observed cycloheximide effect. 

Interesting as it is, the study of transporters for amino acids and other nitrogenous nutrients in Saccharomyces cerevisiae is a tricky field. Many difficulties must be circumvented to avoid trivial errors. These practical problems are linked with several features of eukaryotic uptake systems, the first being the multiplicity of permeases which transport a given substrate. In relation to this, a major point is to make certain that one is not studying more than one uptake system at a time, and this can hardly be done without genetics. Once individual uptake systems have been identified and separated with the help of genetics, a second difficulty arises, which... 

Saccharomyces cerevisiae 85 copper uptake 290 iron storage 100 zinc uptake 295 scandium 108 selenium xvii... 

Gadd, G. M. and Laurence, O. S. (1996). Demonstration of high-affinity Mn2+ uptake in Saccharomyces cerevisiae specificity and kinetics, Microbiol., 142, 1159-1167. 

The bioreduction of carbonyl compounds with reductases has been exploited for many years, especially in the case of ketones, with baker s yeast Saccharomyces cerevisiae) being the most popular biocatalyst [45]. For instance, yeast treatment of 3-chloropropiophenone affords the expected (lS)-3-chloro-l-phenylpropan-l-ol, which was treated with trifluorocresol in tertrahydrofuran in the presence of tri-phenylphosphine and diethyl azodicarboxylate at room temperature to give (3R)-l-chloro-3-phenyl-3-[4-(trifluoromethyl)phenoxy]propane and the later reaction with methylamine leads to (R)-fluoxetine that is an important serotonin uptake inhibitor (Scheme 10.19) [46]. 

These optical probes are the most universally applicable in situ devices for on-line biomass monitoring up to now [15,16]. Konstaninov et al. [17] tested several absorbance and scattering sensors for real-time biomass concentration monitoring in mammalian cell cultivation processes and Hatch and Veilleux [18] compared optical density probes with oxygen uptake rates, packed cell volume, and off-line cell mass monitoring in commercial fed-batch fermentations of Saccharomyces cerevisiae [19]. In order to minimize influencing effects, special chemometric data treatment is necessary [20]. 

Several site-directed mutations were carried out with a new member of the blue oxidases , the Fet3p protein from Saccharomyces cerevisiae which is involved in iron trafficking. The protein oxidizes Fe2+ to Fe3+ as first step in the iron uptake chain. The mutations were targeted to block this ferroxidase activity and thus to identify the residues involved in iron binding. The respective mutants showed no perturbed type 1 sites.91... 

Brendel, M. (1976) A simple method for the isolation and characterization of thy-midylate uptaking mutants in Saccharomyces cerevisiae. Mol. Gen. Genet. 147, 209-215. 

Perez-Corona, T., Y. Madrid, and C. Camara. 1997. Evaluation of selective uptake of selenium (Se(IV) and Se(VI)) and antimony (Sb(III) and Sb(V)) species by Baker s yeast cells (Saccharomyces cerevisiae). Anal. Chim. Acta 345 249-255. 

Mauricio, J. C., Ortega, J. M., and Salmon, J. M. (1995). Sugar uptake by three strains of Saccharomyces cerevisiae during alcoholic fermentation at different initial ammoniacal nitrogen concentrations. Acta Horticult. 388,197-202. 

Breeuwer, P., Drocourt, J. L, Bunschoten, N., Zwietering, M. H., Rombouts, F. M. and Abee, T. Characterization of uptake and hydrolysis of fluorescein diacetate and carboxyfluorescein diacetate by intracellular esterases in Saccharomyces cerevisiae, which result in accumulation of fluores-... 

Wieczorke, R., S. Krampe, T. Weierstall, K. Freidel, C.P. Hollenberg, and E. Boles (1999). Concurrent knock-out of at least 20 transporter genes is required to block uptake of hexoses in Saccharomyces cerevisiae. FEES Lett. 464 123-128. 

There was some evidence for the possible involvement of PolyPs localized in the cell periphery in the uptake and phosphorylation of sugars as energy and phosphate donors (Van Steveninck and Booij, 1964 Hofeler et al, 1987). Later, studies of the mechanisms of transport-associated phosphorylation of 2-deoxy-D-glucose in the yeast Kluyveromyces marxianus (Schuddemat et al, 1989b) and Saccharomyces cerevisiae (Schuddemat et al, 1990) resulted in the conclusion that PolyPs seem to replenish the Pj pool and therefore had an indirect role in sugar transport. 

Fig. 3. Mad activates the expression of three gene products involved in high-affinity copper ion uptake in Saccharomyces cerevisiae. Two genes encode Cu ion permeases Ctrl and Ctr3. The third is one of two metalloreductases that reduce Cu(II) ions prior to uptake. Mad is a transcriptional activator in Cu-deficient yeast cells.

Fig. 14. Redox cycling in the uptake of copper and iron. The lower valent state species is substrate for uptake of copper and iron. The system in the yeast Saccharomyces cerevisiae is diagrammed. The Frel protein reduces environmental Cu " and Fe +. The cuprous ion is substrate for the copper permease, Ctrip. Fe + is substrate for Fet3p its oxidation to Fe + is an obligate step in iron uptake through Ftrlp. Exogenous ferric iron is not taken up by yeast cells unless it is cycled through the ferrireduction-ferrox-idation reactions catalyzed by Frelp and FetSp.

Dancis, A., Klausner, R. D., Hinnebusch, A. G., and Barriocanal, J. G. (1990). Genetic evidence that ferric reductase is required for iron uptake in Saccharomyces cerevisiae. Mol. Cell. Biol. 10, 2294-2301. 

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