Properties of the sugar carrier in Baker's yeast

Haškovec, C

doi:10.1007/bf02866856

Cited by 42 publications

(20 citation statements)

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“…These results, however, are in contrast with the previous report that constitutive galactose transport is a low-affinity facilitated diffusion process (7,31). Other mechanisms of galactose transport in induced cells, including associated phosphorylation (31) and facilitated diffusion (16,18,23), have been proposed. The results reported in this paper suggest a role of ATP for lowand high-affinity inducible transport.…”

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confidence: 91%

Allelism of IMP1 and GAL2 genes of Saccharomyces cerevisiae

et al. 1992

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Cloning and characterization of the previously described Saccharomyces cerevisiae IMP) gene, which was assumed to be a nuclear determinant involved in the nucleomitochondrial control of the utilization of galactose, demonstrate allelism to the GAL2 gene. Galactose metabolism does not necessarily involve the induction of the specific transport system coded by GAL2/IMP1, because a null mutant takes up galactose and grows on it. Data on galactose uptake are presented, and the dependence on ATP for constitutive and inducible galactose transport is discussed. These results can account for the inability of impl/gal2 mutants to grow on galactose in a respiration-deficient background. Under these conditions, uptake was affected at the functional level but not at the biosynthetic level.In Saccharomyces cerevisiae, conversion of exogenous galactose to endogenous glucose 6-phosphate requires a galactose permease, encoded by the GAL2 gene, and the enzymes of the Leloir pathway (galactokinase, transferase, epimerase, and phopshoglucomutase, encoded by GAL1, GAL7, GAL10 and GAL5, respectively). The expression of these genes is coregulated; it is induced by galactose and repressed by glucose (14,22). The rapid response of induction is mediated by the activities of at least three trans-acting regulatory genes: GAL4, GAL80, and GAL3 (14). Moreover, glucose inactivates preexisting permease molecules, a process termed catabolite inactivation (12, 14).As originally claimed by Spiegelman (27), galactose utilization in some strains depends on mitochondrial function. The mitochondrial dependency appears to be mediated through the modulation of nuclear gene activity. In fact, (i) strains with mutations of either structural or regulatory genes (GAL1, GAL2, GAL3, GAL4, and GAL5) grow on galactose under respiration-sufficient (RS) conditions but not under respiration-deficient (RD) conditions (1, 9), and (ii) mitochondrial mutants derived from a number of strains that can grow and utilize galactose are unable to use this sugar (1,8,10,34). It has been suggested that gal3 and galS mutants can use galactose because proteins encoded by other genes share some function (GALl with GAL3 and PGMJ with GAL5) (3, 11). The relationship between alternative functions and the mitochondrial function remains to be established (2). Genetic analysis of the strain differences of the mitochondrial mutants indicates that mitochondrial changes alter the activity or expression of nuclear genes involved in the uptake and use of sugars (1,33).In particular, strains carrying the IMP1 allele can grow on and ferment galactose under both RS and RD conditions or in the presence of a mitochondrial inhibitor such as ethidium bromide or erythromycin. On the contrary, strains carrying the recessive allele impl can grow on and ferment galactose only under RS conditions. In the presence of ethidium bromide, galactose uptake and fermentation are blocked in impl mutants, indicating that the impl mutation makes galactose uptake dependent upon mitochondrial function (1).In an a...

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confidence: 91%

Allelism of IMP1 and GAL2 genes of Saccharomyces cerevisiae

et al. 1992

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“…The second phase is a decreased rate of loss which may result in a relatively high retention of sugar even after 3 hr or more. Such exits have also been described for other sugars [5,10, 11 ]. Sorbose is normally transported across yeast membranes by a process of facilitated diffusion not accompanied by accumulation [1,14].…”

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confidence: 73%

Membrane changes in yeast cells caused by sulfhydryl reagents and accompanied by a selective release of sugar

Spoerl¹

1969

J. Membrain Biol.

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Iodoacetic acid or N-ethylmaleimide included in cell suspensions during measurements of sorbose exit from yeast cells caused sorbose efflux to occur at a uniform rate in contrast to the usual two-phase exit. Cells pretreated with these agents were still capable of sugar uptake, but the entire efflux now occurred at the usual initial rate. Microscopically, the vacuoles of treated cells were observed to be altered or disrupted. Vacuolar effects occurred before methylene blue was able to penetrate the external cell membrane and stain the cells. Vacuoleless cells also allowed a single rate of sorbose efflux. The selective effect upon intracellular membranes is interpreted as a disruption of the boundaries of an internal sugar compartment with the result that sugar exits from the cell at a rate controlled only by the external membrane.

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“…A pure strain of Saccharomyces cerevisiae isolated from distillery yeast was used as described before [2].…”

Section: And Methodsmentioning

confidence: 99%

“…It has been reported in a previous paper [2] and by Cirillo [3] that growth of Saccharomyces cerevisiae on D-galactose induced the de novo synthesis of both the galactose-utilizing enzymes and the galactose membrane carrier, the carrier showing a preference for monosaccharides with an axial hydroxyl group a t carbon 4 of the C l chair conformation of the monosaccharide. The induction of the galactose carrier (or its component) thus involves the synthesis of a protein interacting with D-galactose which should be most probably localized in the plasmalemma.…”

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Attempts at Purifying the Galactose Carrier from Galactose‐Induced Baker's Yeast

Haškovec¹

1969

European Journal of Biochemistry

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1. An attempt was made to isolate the protein associated with the formation of the inducible D-galactose-transporting system in baker's yeast. Of the several fractions obtained by centrifugation of homogenized yeast cells a t different speeds only the fraction sedimenting a t 40000 x g and containing a predominance of membranes was found to bind D-galactose, the dissociation constant being 0.2-0.6 mM. No galactokinase activity was found in this fraction.2. The membrane proteins were solubilized using various technique but the amount of sugar bound by the solubilized proteins was lower than that bound by the intact membranes, the most promising appearing to be treatment with 1 M NaI.3. Membrane proteins labelled by a double-labelling technique were solubilized with 1 M NaI and separated on DEAE-cellulose in a linear gradient of NH4HC0,. A peak of unequal labelling with 14C and 3H was identified both in normal baker's yeast and in a galactokinase-less mutant and assumed to represent the inducible galactose carrier or a part of its transport system.It has been reported in a previous paper RESULTS Isolation of the D-Gahtose Binding Subcellular FractionHarvested yeast cells were washed three times with distilled water and resuspended in a buffer containing 5 mM KH,P04 and 5 mM MgCl, a t pH 5.8.The suspension was homogenized with Ballotini glass beads no. 12 (2 parts of dry beads to 1 part of suspension) for 1 min in a tightly sealed cuvette provided with a stainless-steel propeller and driven by a MSE homogenizer a t its maximum speed. The glass vessel was immersed in an ice bath. The glass beads were removed by filtration and washed several times with the above buffer. The combined filtrates and washings were fractionated a t + 3" in a small bench centrifuge and in a MSE 50 centrifuge as follows: 20 min a t 1500 xg (intact cells, cell walls and heavy debris, including some mitochondria), 35 min at 40000xg (membranes contaminated with some mitochondria), 45 min a t 100000 x g (ribosomes). The individual sediments were washed with buffer and their binding affinity for D-galactose was tested as follows: 0.2 ml

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Properties of the sugar carrier in Baker's yeast

Cited by 42 publications

References 3 publications

Allelism of IMP1 and GAL2 genes of Saccharomyces cerevisiae

Allelism of IMP1 and GAL2 genes of Saccharomyces cerevisiae

Membrane changes in yeast cells caused by sulfhydryl reagents and accompanied by a selective release of sugar

Attempts at Purifying the Galactose Carrier from Galactose‐Induced Baker's Yeast

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