Homology modeling of the serotonin transporter: insights into the primary escitalopram-binding site.

The serotonin transporter (SERT) is one of the neurotransmitter transporters that plays a critical role in the regulation of endogenous amine concentrations and therefore is an important target for therapeutic agents affecting the central nervous system. The recently published, high resolution X-ray structure of the closely related amino acid transporter, Aquifex aeolicus leucine transporter (LeuT), provides an opportunity to develop a three-dimensional model of the structure of SERT. We present herein a homology model of SERT using LeuT as the template and containing escitalopram as a bound ligand. Our model explains selectivities known from mutational studies and varying ligand data, which are discussed and illustrated in the paper.