Evidence for a proton/sugar symport in the yeast Rhodotorula gracilis (glutinis)

Abstract

1. The uptake of monosaccharides and polyols in the obligatory aerobic yeast Rhodotorula gracilis (glutinis) was accompanied by proton uptake. 2. The halfsaturation constant of transport, KT, depended on pH, changing from about 2mM at pH4.5 to 80mM at pH8.5 for D-xylose; this change of the effective carrier affinity was reversible. 3. The apparent dissociation constant of the monosaccharide carrier was estimated at pKa 6.75. 4. At pH8.5, when the pH gradient across the cell membrane vanished, no sugar accumulation was demonstrable. 5. The half-saturation constants of sugar uptake and H+ co-transport were very similar to each other, the latter obviously being controlled by the former. 6. The H+/sugar stoicheiometry remained constant under various physiological conditions; it amounted to one H+ ion per sugar molecule taken up. 7. The data are interpreted as a strong piece of evidence in favour of the active monosaccharide transport in R. gracilis (glutinis) being an H+-symport energized by the electrochemical gradient of H+ across the plasma membrane of the yeast.

Continuous-culture study of the regulation of glucose and fructose transport in Kluyveromyces marxianus CBS 6556

“…Facilitated diffusion and proton-sugar symport have been established for many different types of yeast (8,16,19,20). Moreover, it is claimed that glucose transport in Saccharomyces cerevisiae and Kluyveromyces marxianus can proceed through a phosphotransferase (10,17).…”

Effect of ethanol on cell growth, metabolism and cation fluxes in the yeast Metschnikowia reukaufii

“…S. cerevisiae (Eddy, 1978 ; Sigler et al, 198 l), Schizosaccharomyces pombe (Foury et al, 1977) and Rhodotorula glutinis (Hofer & Misra, 1978), glucose induced a strong acidification of M . reukauji cell suspensions (Fig.…”

Isolation and characterization of a Rhodotorula glutinis mutant defective in glucose transport

“…The obligatory aerobic yeast Rhodotorula glutinis is capable of transporting a wide variety of metabolizable and non-metabolizable monosaccharides by an electrogenic H+-symport (Hofer & Misra, 1978 ;Hauer & Hofer, 1978). Early results suggested that -the uptake of monosaccharides was mediated by a common membrane transport system, displaying a high substrate specificity for D-glucose (Kotyk & Hofer, 1965;Hofer & Kotyk, 1968;Hofer, 1970;Hofer & Dahle, 1972).…”