The Bin/Amphiphysin/Rvs (BAR) domain, a dimerization module that binds membranes and detects membrane curvature
BAR domains are dimerization, lipid binding and curvature sensing modules found in many different proteins with diverse functions including organelle biogenesis, membrane trafficking or remodeling, and cell division and migration. Mutations in BAR containing proteins have been linked to diseases and their inactivation in cells leads to altered membrane dynamics. A BAR domain with an additional N-terminal amphipathic helix (an N-BAR) can drive membrane curvature. These N-BAR domains are found in amphiphysins and endophilins, among others. BAR domains are also frequently found alongside domains that determine lipid specificity, such as the Pleckstrin Homology (PH) and Phox Homology (PX) domains which are present in beta centaurins (ACAPs and ASAPs) and sorting nexins, respectively. A FES-CIP4 Homology (FCH) domain together with a coiled coil region is called the F-BAR domain and is present in Pombe/Cdc15 homology (PCH) family proteins, which include Fes/Fes tyrosine kinases, PACSIN or syndapin, CIP4-like proteins, and srGAPs, among others. The Inverse (I)-BAR or IRSp53/MIM homology Domain (IMD) is found in multi-domain proteins, such as IRSp53 and MIM, that act as scaffolding proteins and transducers of a variety of signaling pathways that link membrane dynamics and the underlying actin cytoskeleton. BAR domains form dimers that bind to membranes, induce membrane bending and curvature, and may also be involved in protein-protein interactions. The I-BAR domain induces membrane protrusions in the opposite direction compared to classical BAR and F-BAR domains, which produce membrane invaginations. BAR domains that also serve as protein interaction domains include those of arfaptin and OPHN1-like proteins, among others, which bind to Rac and Rho GAP domains, respectively.