The role of tryptophan cation–pi interactions on ammonia transport through the AmtB ammonia channel

.The high-resolution structure of Escherichia coli AmtB ammonia/ammonium channel and proteoliposome functional analysis has provided sufficient information to propose a permeation theory for this integral membrane channel protein. The role of cation–pi interactions at the periplasmic vestibule of the channel is proposed and integrated with molecular and quantum mechanical dynamics simulations and calculations. The structural and simulation data closely reinforce each other and point to cation–pi interactions as one of the primary mechanisms of ligand recruitment within the channel vestibule.