Endocytosis and intracellular transport involve several mechanistic steps:

1. For the internalisation of cargo molecules, the membrane needs to bend to form a vesicular structure, which requires membrane curvature and a rearrangement of the cytoskeleton;
2. Following its formation, the vesicle has to be pinched off the membrane;
3. The cargo has to be subsequently transported … expand

Endocytosis and intracellular transport involve several mechanistic steps:

1. For the internalisation of cargo molecules, the membrane needs to bend to form a vesicular structure, which requires membrane curvature and a rearrangement of the cytoskeleton;
2. Following its formation, the vesicle has to be pinched off the membrane;
3. The cargo has to be subsequently transported through the cell and the vesicle must fuse with the correct cellular compartment.

Members of the Amphiphysin protein family are key regulators in the early steps of endocytosis, involved in the formation of clathrin-coated vesicles by promoting the assembly of a protein complex at the plasma membrane and directly assist in the induction of the high curvature of the membrane at the neck of the vesicle. Amphiphysins contain a characteristic domain, known as the BAR (Bin-Amphiphysin-Rvs)-domain, which is required for their in vivo function and their ability to tubulate membranes [ PUBMED:14993925 ].

The crystal structure of these proteins suggest the domain forms a crescent-shaped dimer of a three-helix coiled coil with a characteristic set of conserved hydrophobic, aromatic and hydrophilic amino acids. Proteins containing this domain have been shown to homodimerise, heterodimerise or, in a few cases, interact with small GTPases.