The Bin/Amphiphysin/Rvs (BAR) domain of Oligophrenin-1
BAR domains are dimerization, lipid binding and curvature sensing modules found in many different proteins with diverse functions. Oligophrenin-1 (OPHN1) is a GTPase activating protein (GAP) with activity towards RhoA, Rac, and Cdc42, that is expressed in developing spinal cord and in adult brain areas with high plasticity. It plays a role in regulating the actin cystoskeleton as well as morphology changes in axons and dendrites, and may also function in modulating neuronal connectivity. Mutations in the OPHN1 gene causes X-linked mental retardation associated with cerebellar hypoplasia, lateral ventricle enlargement and epilepsy. OPHN1 contains an N-terminal BAR domain, followed by a Pleckstrin homology (PH) domain, and a Rho GAP domain. BAR domains form dimers that bind to membranes, induce membrane bending and curvature, and may also be involved in protein-protein interactions.