In a screening for cDNAs encoding proteins similar to the sodium-coupled glutamate transporter GLAST1, Hofmann et al. isolated a cDNA clone encoding a protein that turned out to be identical to the neutral amino acid transporter ASCT1. The member of the GLAST-related transporter family did not transport glutamate or aspartate but alanine, serine, cysteine, and threonine instead. The open reading frame of 1,572 basepairs encodes 524 amino acid residues distributed over 8 exons spanning at least 40 kb of genomic DNA. The gene for ASCT1, designated SLC1A4, was assigned to 2p15-p13 by fluorescence in situ hybridization. The gene structure was not related to any previously characterized transporter gene. Transport is associated with a chloride channel activity that is thermodynamically uncoupled from amino acid transport.