High impact information on GUP1

• Fps1, a yeast member of the MIP family of channel proteins, is a facilitator for glycerol uptake and efflux and is inactive under osmotic stress [1].
• GUP1 is highly conserved among fungi and protozoa and the gup1Delta phenotype is partially corrected by GUP1 homologues of Aspergillus fumigatus and Trypanosoma cruzi [2].
• GUP1 function depends on the active site histidine of the MBOAT motif [2].
• To identify genes involved in active glycerol uptake in Saccharomyces cerevisiae we screened a deletion mutant collection comprising 321 genes encoding proteins with 6 or more predicted transmembrane domains for impaired growth on glycerol medium [3].
• GUP1 and its close homologue GUP2, encoding multimembrane-spanning proteins involved in active glycerol uptake in Saccharomyces cerevisiae [4].

Biological context of GUP1

• Previous studies evidenced in Saccharomyces cerevisiae the activity of a H(+)/glycerol symport, derepressed by growth on non-fermentable carbon sources, later associated with GUP1 and GUP2 genes [5].
• Expression studies of GUP1 and GUP2, genes involved in glycerol active transport in Saccharomyces cerevisiae, using semi-quantitative RT-PCR [6].
• Another open reading frame (ORF), YPL189w, presenting a high degree of homology to YGL084c, similarly appears to be involved in active glycerol uptake in salt-containing glucose-based media in strains deficient in glycerol production [4].
• Gup1p belongs to the list of yeast proteins rapidly down-regulated by changing the carbon source in the culture medium, in agreement with the concept that post-translational modifications triggered by glucose affect proteins of peripheral functions [7].

Anatomical context of GUP1

• Glycerol-uptake experiments showed that the permeability of the yeast plasma membrane for glycerol consists of an Fps1-independent component probably due to simple diffusion and of an Fps1-dependent component representing facilitated diffusion [1].
• However, spheroplasts prepared from the strain overexpressing Fps1p showed enhanced glycerol uptake, suggesting that Fps1p becomes active only upon insertion in the plasma membrane [8].
• Absence of Gup1p in Saccharomyces cerevisiae results in defective cell wall composition, assembly, stability and morphology [9].
• The Gup1p tagged with GFP is a functional glycerol transporter localized at the plasma membrane and endoplasmic reticulum levels of induced cells [7].
• The immunoelectron microscopy assays of cells expressing either Gup1-GFP or GFP-Gup1 fusions suggested the Gup1p membrane topology: the N-terminus lies in the periplasmic space, whereas its C-terminal tail has an intracellular location [7].

Associations of GUP1 with chemical compounds

• These results suggest different roles for Gup1/2p than glycerol transport [5].
• Eadie-Hofstee plots of glycerol uptake in wild-type Saccharomyces cerevisiae W303-1A grown on glucose showed the presence of both saturable transport and simple diffusion, whereas an fps1delta mutant displayed only simple diffusion [10].
• In contrast, the phenylalanine residue, which is believed to position substrates near the conserved arginine, was not required for either arsenic trioxide or glycerol uptake [11].
• From these results, it is suggested that DL1 has distinct metabolic characteristics including enhanced metabolic activities both in glycerol uptake and the glyoxylate bypass cycle, as compared to A16 [12].

Analytical, diagnostic and therapeutic context of GUP1

• Using semi-quantitative RT-PCR, GUP1 and GUP2 transcription was measured [6].
• The subcellular localization and functional expression of biologically active Gup1-GFP chimaeras was monitored by confocal laser scanning and electron microscopy, thus supplying the first study of GUP1 dynamics in live yeast cells [7].

References