Sertraline is a selective serotonin reuptake inhibitor (SSRI) which is widely prescribed to treat depression. It functions by inhibiting the presynaptic plasma membrane serotonin transporter (SERT). A bacterial analogue of mammalian SERT is LeuT, which is a leucine transporter used to study interactions between SERT proteins and SSRI drugs.

There is a sole site of SSRI drug binding in the bacterial LeuT leucine transpoter.

The active site contains a halogen binding pocket that is formed by Leu25, Gly26, Leu29, Arg30, Tyr108, Ile111 and Phe 253.

The sertraline drug molecule (yellow) binds to the extracellular vestibule in the protein in such a way that the two chlorine atoms (green) on the phenyl ring insert into this halogen binding pocket.

Two sodium cations (purple) are also present near the active site. These have been suggested to stabilize the active site residues in order for the chlorines of sertraline to bind effectively in the halogen binding pocket.