An allosteric pore model for sugar transport in human erythrocytes.

Glucose transport in human erythrocytes is characterized by a marked asymmetry in the V and Km values for entry and for exit. In addition, they show a high Km and a high V for equilibrium exchange that low Km values for infinite cis and for infinite trans exit and entry. An allosteric pore model has been proposed to account for these characteristics. In this model, substrate-induced conformational changes destabilize the interfaces between protein subunits (the pore gates). Pores doubly occupied from inside destabilize the transport gates and result in high Km and high V transport parameters. This effect is less marked when pores are doubly occupied from outside and therefore transport asymmetry results.