The one-site model of human erythrocyte glucose transport: testing its predictions using network thermodynamic computer simulations.
Network thermodynamic computer simulations were carried out using parameters experimentally derived by Lowe and Walmsley ((1987) Biochim. Biophys. Acta 903, 547-550) for two tests of the one-site model of human erythrocyte glucose transport. In the temperature-jump experiment, the simulations predicted the amplitude and relaxation time of accelerated uptake, but underestimated the net uptake due to an unexpectedly low measured basal rate. In the maltose-acceleration experiment, the dissociation constant of maltose was assessed at 0 degrees C by measuring the inhibitory effects of maltose on both cytochalasin B binding and on 3-O-methylglucose uptake, and using this value (52 mM) to calculate the dissociation constant (2.9 mM). The simulated experiment then did show a transient acceleration in uptake comparable in magnitude to that observed experimentally, except that the relaxation time was more than 10-fold longer in the simulations. Measurements of the temperature dependence of the inhibition of cytochalasin B binding by maltose and 3-O-methylglucose indicated that apparent sugar affinity is sensitive to carrier orientation at low temperatures, whereas at more physiologic temperatures the intrinsic dissociation constant predominated.
May
J M
JM
Department of Medicine, Vanderbilt University, School of Medicine, Nashville, TN 37232.
D019325:3-O-Methylglucose; D001692:Biological Transport; D003198:Computer Simulation; D003571:Cytochalasin B / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008320:Maltose / Q000378:metabolism; D008757:Methylglucosides / Q000378:metabolism; D008954:Models, Biological; D013696:Temperature; D013816:Thermodynamics
D008757:Methylglucosides; D019325:3-O-Methylglucose; D003571:Cytochalasin B; D008320:Maltose; D005947:Glucose