Proton-control of transitions in an amino-acid transporter (Biophysical Journal)

Amino acid transport into the cell is often coupled to the proton electrochemical gradient, as found in the solute carrier (SLC) 36 family of proton coupled amino acid transporters (PATs). Although no structure of a human PAT exists, the crystal structure of a related homolog from bacteria, GkApcT, has recently been solved in an inward-occluded state and allows an opportunity to examine how protons are coupled to amino acid transport. Our working hypothesis is that release of the amino acid substrate is facilitated by deprotonation of a key glutamate residue (E115), located at the bottom of the binding pocket and which forms part of the intracellular gate, allowing the protein to transition from an inward-occluded to an inward-open conformation.