Most ABC importers employ a soluble substrate-binding protein (SBP) to capture the ligand and donate the molecule to the translocator. The SBP can be a soluble periplasmic protein or tethered to the membrane via a lipid moiety or protein anchor or fused to the translocator. In the hybrid ABC transporters, multiple substrate-binding domains (SBDs) can be fused in tandem and provide several extracytoplasmic substrate-binding sites. The substrate is transferred from the SBP to the membrane domain, which translocates the substrate via alternating access of a membrane-embedded substrate-binding pocket. A subset of ABC transporters, known as the energy-coupling factor (ECF) transporters, employs a membrane-embedded S-component to capture the substrate. The S-component guided by the ECF module transports the substrate over the membrane via a so-called toppling mechanism. An overview of the mechanisms of transport by the different types of ABC importers is presented, together with structural information about the proteins.
|Title of host publication||ABC Transporters - 40 Years on|
|Editors||Anthony M. George|
|Number of pages||34|
|Publication status||Published - 17-Dec-2015|