Figure 3. Cooperativity between the individual GLUT1 protomers.

(A) In the tetrameric arrangement, there appears to be a concerted conformational rearrangement of the individual protomers. Substrate binding to the substrate-binding sites of two protomers exposed on either side of the membrane followed by transport results in the conformational rearrangement of all four protomers such that two protomers are always inward facing (IF) and two protomers are always outward facing (OF). (B) In contrast, in a dimer arrangement, the two protomers are associated but operate independently of one another.