Analysis of the H+/sugar symport in yeast under conditions of depolarized plasma membrane.
H+/sugar symport in the obligatory aerobic yeast Rhodotorula glutinis was analyzed under conditions where the plasma membrane was selectively depolarized by the lipophilic cation tetraphenylphosphonium (TPP+). Control experiments showed that this treatment did not impair the transmembrane delta pH, the cell energy charge, and the function of plasma membrane H+-ATPase. The kinetic data were fitted to elementary functions derived from a model constructed on the basis of some simplifying premises for ordered (either C + H+ + S or C + S + H+) and random reaction mechanisms. In addition, the comparison of the kinetic parameters in fully energized and depolarized cells provided information about the free carrier charge. It was concluded that the binding sequence of formation of the ternary carrier/H+/substrate complex follows a random mechanism and that the carrier bears a negative charge.
Severin
J
J
Botanisches Institut der Universität, Bonn, FRG.
Langel
P
P
Höfer
M
M
D001693:Biological Transport, Active; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D004734:Energy Metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D003904:Mitosporic Fungi / Q000378:metabolism*; D008956:Models, Chemical; D009861:Onium Compounds / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000494:pharmacology; D010101:Oxygen Consumption; D011522:Protons; D012248:Rhodotorula / Q000187:drug effects / Q000378:metabolism*
D003837:Deoxy Sugars; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D011522:Protons; D003847:Deoxyglucose; C013289:tetraphenylphosphonium