The Bin/Amphiphysin/Rvs (BAR) domain of Arfaptin-like proteins, a dimerization module that binds and bends membranes
The BAR domain of Arfaptin-like proteins, also called the Arfaptin domain, is a dimerization, lipid binding and curvature sensing module present in Arfaptins, PICK1, ICA69, and similar proteins. Arfaptins are ubiquitously expressed proteins implicated in mediating cross-talk between Rac, a member of the Rho family GTPases, and Arf (ADP-ribosylation factor) small GTPases. Arfaptins bind to GTP-bound Arf1, Arf5, and Arf6, with strongest binding to GTP-Arf1. Arfaptins also binds to Rac-GTP and Rac-GDP with similar affinities. The Arfs are thought to bind to the same surface as Rac, and their binding is mutually exclusive. Protein Interacting with C Kinase 1 (PICK1) plays a key role in the trafficking of AMPA receptors, which are critical for regulating synaptic strength and may be important in cellular processes involved in learning and memory. Islet cell autoantigen 69-kDa (ICA69) is a diabetes-associated autoantigen that is involved in membrane trafficking at the Golgi complex in neurosecretory cells. ICA69 associates with PICK1 through their BAR domains to form a heterodimer which is involved in regulating the synaptic targeting and surface expression of AMPA receptors. BAR domains form dimers that bind to membranes, induce membrane bending and curvature, and may also be involved in protein-protein interactions.