The mechanism of antiporter transport involves several key steps and a series of conformational changes that are dictated by the structural element described above:
# The substrate binds to its specific binding site on the extracellular side of the plasma membrane, forming a temporary substrate-bound open form of the antiporter.
# This becomes an occluded, substrate-bound state that is still facing the extracellular space.
# The antiporter undergoes a conformational change to become an occluded, substrate-bound protein that is now facing the cytosol. As it does so, it passes through a temporary fully-occluded intermediate stage.
# The substrate is released from the antiporter as it takes on an open, inward-facing conformation.
# The antiporter can now bind to its second substrate and transport it in the opposite direction by taking on its transient substrate-bound open state.
# This is followed by an occluded, substrate-bound state that is still facing the cytosol, a conformation change with a temporary fully-occluded intermediate stage, and a return to the antiporter's open, outward-facing conformation.
# The second substrate is released and the antiporter can return to its original conformation state, where it is ready to bind to new molecules or ions and repeat its transport process.