Abstract
Deoxyglucose greatly accelerates the rate of reaction between fluorodinitrobenzene and the sugar transfer system of human erythrocytes, whereas maltose reduces the rate. Both sugars act by forming a 1:1 complex with carrier. It is shown that maltose, which does not enter the cells, competes with deoxyglucose both outside the cells and inside. The fluorodinitrobenzene concentration within the cells is identical to that in the suspending medium. These observations are inconsistent with a transport model involving a pair of carrier units in a single pore, each restricted to one surface of the membrane, where each unit undergoes conformational changes independently of the other. They are consistent with three models: (i) a single carrier alternately exposed at either membrane surface, though other evidence militates gainst this; (ii) a symmetrical pair of carrier units undergoing linked conformational changes following sugar binding; (iii) a highly unsymmetrical mechanism in which only the external member of a carrier pair is inactivated by fluorodinitrobenzene or activated towards fluorodinitrobenzene by bound sugar.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Biomembranes
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