tight coupling of monosaccharide transport and metabolism inRhodotorula gracilis
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A variety of agents have been applied to separate the uphill, metabolically linked transport of monosaccharides from facilitated diffusion inRhodotorula gracilis. The substances used were iodoacetamide, 2,4-dinitrophenol, carbonyl cyanide m-chlorophenylhydrazone, sodium azide, sodium fluoride and heavy-metal cations, including Cd2+, Hg2+, Cu2+, UO2+ 2, La3+ and Th4+. No agent examined led to such separation. There was always either a complete inhibition of both cell metabolism (or uncoupling of oxidative phosphorylation) and the transport mechanism or the transport of sugars uphill persisted (when the metabolism was only partly inhibited). It is concluded that the monosaccharide transporting system inRhodotorula gracilis is tightly coupled to cell metabolism and cannot operate without sufficient energy supply even in cases when no uphill movement is involved.
KeywordsIodoacetamide Sodium Fluoride Sugar Uptake Uranyl Nitrate Carbonyl Cyanide
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