Glucose transporter conformational changes

Peerce, B.E. Wright, E.M. (1984). Sodium-induced conformational changes in the glucose transporter of intestinal brush borders. J. Biol. Chem. 259, 14105-14112. 

Another form of facilitated diffusion involves membrane proteins called carriers (sometimes referred to as passive transporters). In carrier-mediated transport, a specific solute binds to the carrier on one side of a membrane and causes a conformational change in the carrier. The solute is then translocated across the membrane and released. The red blood cell glucose transporter is the best-characterized example of passive transporters. It allows D-glucose to diffuse across the red blood cell membrane for use in glycolysis and the pentose phosphate pathway. Facilitated diffusion increases the rate at which certain solutes move down their concentration gradients. This process cannot cause a net increase in solute concentration on one side of the membrane. 

Each type of transport protein or carrier binds a specific molecule. As a result of this binding, a conformational change occurs in the carrier, which results in translocadon of the ligand across the membrane. The rbc glucose transporter is an example of such a carrier. 

Figure 7-21 depicts the current model of transport by Na /glucose symporters. This model entails conformational changes In the protein analogous to those that occur in uniport transporters, such as GLUTl, which do not require a cotransported Ion (see Figure 7-4). Binding of all substrates to their sites on the extracellular domain Is required before...

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