INHIBITIONS OF SUGAR-TRANSPORT PRODUCED BY LIGANDS BINDING AT OPPOSITE SIDES OF THE MEMBRANE - EVIDENCE FOR SIMULTANEOUS OCCUPATION OF THE CARRIER BY MALTOSE AND CYTOCHALASIN-B
INHIBITIONS OF SUGAR-TRANSPORT PRODUCED BY LIGANDS BINDING AT OPPOSITE SIDES OF THE MEMBRANE - EVIDENCE FOR SIMULTANEOUS OCCUPATION OF THE CARRIER BY MALTOSE AND CYTOCHALASIN-B
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DOI：
10.1021/bi00230a015
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发表时间：
1991-04-23
期刊：
影响因子：
2.9
通讯作者：
HELGERSON, AL
中科院分区：
文献类型：
--
作者：
CARRUTHERS, A;HELGERSON, AL
This study examines inhibitions of human erythrocyte D-glucose uptake at ice temperature produced by maltose and cytochalasin B. Maltose inhibits sugar uptake by binding at or close to the sugar influx site. Maltose is thus a competitive inhibitor of sugar uptake. Cytochalasin B inhibits sugar transport by binding at or close to the sugar efflux site and thus acts as a noncompetitive inhibitor of sugar uptake. When maltose is present in the uptake medium, K(i(app)) for cytochalasin B inhibition of sugar uptake increases in a hyperbolic manner with increasing maltose. When cytochalasin B is present in the uptake medium, K(i(app)) for maltose inhibition of sugar uptake increases in a hyperbolic manner with increasing cytochalasin B. High concentrations of cytochalasin B do not reverse the competitive inhibition of D-glucose uptake by maltose. These data demonstrate that maltose and cytochalasin B binding sites coexist within the glucose transporter. These results are inconsistent with the simple, alternating conformer carrier model in which maltose and cytochalasin B binding sites correspond to sugar influx and sugar efflux sites, respectively. The data are also incompatible with a modified alternating conformer carrier model in which the cytochalasin B binding site overlaps with but does not correspond to the sugar efflux site. We show that a glucose transport mechanism in which sugar influx and sugar efflux sites exist simultaneously is consistent with these observations.
