1. Concerted model for maltose transport.
Concerted model for maltose transport. In the absence of maltose, the MalFGK2 transporter rests in a conformation in which the NBD dimer interface is open and the translocation pathway is exposed only to the cytoplasm (P-closed conformation). On binding of maltose, the periplasmic maltose-BP undergoes a conformational change from open to closed, and interaction with the closed maltose-BP in the presence of ATP triggers a global conformational change in which the NBDs close to promote ATP hydrolysis, maltose-BP becomes tightly bound to MalFGK2, and both maltose-BP and MalFGK2 open at the periplasmic surface of the membrane to facilitate the transfer of substrate from maltose-BP to a binding site in the membrane (P-open conformation). Following ATP hydrolysis, which destabilizes the NBD dimer, the transporter returns to the resting state and maltose completes its translocation across the membrane. (Adapted from reference 69 with permission of the publisher. Copyright 2001 National Academy of Sciences, U.S.A.)‏
Amy L. Davidson et al. Microbiol. Mol. Biol. Rev. 2008; doi: /MMBR