The SNF3 gene is required for high-affinity glucose transport in Saccharomyces cerevisiae

Abstract

Glucose uptake mutants have not been previously obtained in Saccharomyces cerevisiae, possibly because there seem to be at least two transport systems, of low and high affinities. We showed that snf3 (sucrose nonfermenting) mutants did not express high-affinity glucose uptake. Furthermore, their growth was completely impaired on low concentrations of glucose in the presence of antimycin A (which blocks respiration).Several genes which complemented the original snJ3 gene were obtained on multicopy plasmids. Some of them, as well as plasmid-carried SNF3 itself, conferred a substantial increase in high-affinity glucose uptake in both snf3 and wild-type hosts. The effects of glucose on the expression of such a plasmid-determined high-affinity uptake resembled those in the wild type. Other genes complementing snJ3 seemed to cause an increase in low-affinity glucose uptake. We suggest that SNF3 may function specifically in high-affinity glucose uptake, which is needed under some conditions of growth on low glucose concentrations. SNF3 itself or the other complementing genes may specify components of the glucose uptake system.The uptake of glucose and fructose in Saccharomyces cerevisiae is mediated by both high (Km = 1 to 2 mM for glucose and 5 to 7 mM for fructose)-and low (Km = 15 to 20 mM for glucose and 50 to 100 mM for fructose)-affinity transport systems (1). Low-affinity uptake appears to occur by constitutive facilitated diffusion. High-affinity uptake, on the other hand, is not expressed in cells grown in the presence of high glucose concentrations (3), and mutant studies revealed that this transport system is under glucose catabolite repression control (L. Bisson, unpublished data).The activity of the high-affinity hexose transport system is dependent upon the activity of glucose-phosphorylating enzymes within the cell. In S. cerevisiae, there are three known enzymes catalyzing the phosphorylation of glucose at the six position: hexokinase A (PI), hexokinase B (Pll), and glucokinase; the hexokinases also catalyze the phosphorylation of fructose (11,12). While triple kinase mutants (hxkl hxk2 glk) lacking all three kinase activities do not display high-affinity uptake of either glucose or fructose (1), a double kinase mutant (hxkl hxk2) lacking both hexokinases A and B but retaining glucokinase lacks high-affinity uptake of fructose but retains high-affinity uptake of glucose (1). Transformation of a triple kinase mutant with a plasmid carrying a gene encoding any one of the kinases (pHXKI, pHXK2, or pGLK) restored high-affinity uptake of glucose; only pHXKI and pHXK2 were able to restore high-affinity uptake of both glucose and fructose (1). High-affinity uptake of a nonphosphorylatable glucose analog, 6-deoxyglucose, was also found to be "kinase dependent," suggesting some role of the kinases in high-affinity uptake other than simple phosphorylation of the substrate (2).Understanding the role of the kinases in kinase-dependent transport as well as the physiological roles of both low-and high-affinity uptake...

Irreversible inactivation of Saccharomyces cerevisiae fructose‐1,6‐bisphosphatase independent of protein phosphorylation at Ser11

“…In this case, no glucose inactivation would occur if the cells were grown on glucose. One such component might be the glucose repressible glucose carrier encoded by the SNF3 gene [28]. The ability of uncouplers to inactivate [29] lends some support to this suggestion, as they might mimic a proton driven glucose uptake, so far unrecognized.…”

Inactivation of the galactose transport system in Saccharomyces cerevisiae

“…With respect to sugars, it is known that maltose [4] as well as glucose transport systems [5] consist of two components that, in the latter case, are controlled differently by catabolite repression [6] and by the presence of hexose kinases [7]. To our knowledge, the existence of several forms in the case of the galactose transport system has not yet been explored.…”

“…Transport systems in Saccharomyces cerevisiae are very often composed of several forms distinguishable by their different affinity constants for the respective substrates [1][2][3][4][5][6][7]. With respect to sugars, it is known that maltose [4] as well as glucose transport systems [5] consist of two components that, in the latter case, are controlled differently by catabolite repression [6] and by the presence of hexose kinases [7].…”

Sugar induced cell death in yeast is dependent on the rate of sugar phosphorylation as determined by Arabidopsis thaliana hexokinase

“…Whether the low-affinity transport (K m is 10 ± 20 mM for glucose and 20 ± 50 mM for fructose) is mediated by transporters or by passive diffusion is as yet unclear (Bisson et al, 1993;Lagunas, 1993;Coons et al, 1995). However, cells with null allele of SNF3 lack the high-affinity hexose transport and neither grow on supplemented media containing 5.5 mM glucose (Bisson et al, 1987;Neigeborn et al, 1986) nor undergo SICD upon incubation in 5.5 mM glucose (Granot and Snyder, 1993) but grow in supplemented media containing 110 mM glucose (Bisson et al, 1987;Neigeborn et al, 1986) and undergo SICD in 110 mM glucose (Granot and Snyder, 1993). Therefore, SICD may occur independently of highaffinity hexose transport.…”

“…Glucose and fructose are transported into yeast cells by high-affinity and by low-affinity transport (for review see Bisson et al, 1993). The high-affinity transport whose K m is 2 mM for glucose and 5 mM for fructose is mediated by several nonessential transporters and sugar receptors like SNF3 (Bisson et al, 1987;Coons et al, 1995;Ozcan et al, 1996;Yang and Bisson, 1996). Whether the low-affinity transport (K m is 10 ± 20 mM for glucose and 20 ± 50 mM for fructose) is mediated by transporters or by passive diffusion is as yet unclear (Bisson et al, 1993;Lagunas, 1993;Coons et al, 1995).…”