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. The primary function of these motifs is to provide a versatile structural framework to mediate the formation of protein-protein interactions. LRRs are present in a variety of proteins with diverse structure and function, including innate immunity and nervous system development. LRRC1 (leucine-rich repeat-containing protein 1), also known as LANO adapter protein or LAP and no PDZ protein, is a 524 amino acid protein that contains 17 LRR repeats. Localized to the cytoplasm and the membrane, LRRC1 is expressed strongly in placenta and testis, with lower levels found in heart, kidney, thyroid, lung, prostate, colon and trachea. LRRC1 interacts with PSD-95 and SAP 97, and may form a complex with SAP 97 and ERBIN. LRRC1 is expressed as two isoforms produced by alternative splicing events.