The leucine-rich (LRR) repeat is a 20-30 amino acid motif that forms a hydrophobic ?/∫ horseshoe fold, allowing it to accommodate several leucine residues within a tightly packed core. All LRR repeats contain a variable segment and a highly conserved segment, the latter of which accounts for 11 or 12 residues of the entire LRR motif. SLITRK3 (SLIT and NTRK-like family, member 3) is a 977 amino acid single-pass type I membrane protein that contains 20 LRR repeats and belongs to the SLITRK family. Expressed at highest levels in cerebral cortex, SLITRK3 is also found in adult and fetal neural tissues and some astrocytic brain tumors. SLITRK3 functions to suppress neurite outgrowth and plays a role in the regulation of neuronal function. SLITRK3 is encoded by a gene that maps to human chromosome 3, which houses over 1,100 genes, including a chemokine receptor (CKR) gene cluster and a variety of human cancer-related gene loci.