Adaptin (AP) are proteins which mediate the formation of vescicles by clathrin-coated pits.
The AP-2 complex is a heterotetramer composed a core domain containing 2 large AP: AP-α or AP-γ and AP-β, a medium-size AP: AP-μ and small AP: AP-σ, 2 appendage domains or EAR. The core domain binds to the membrane and to cargo proteins which should be internalized and the EAR domains bind to clathrin and accessory proteins. There are different AP complexes in mammals.[1]
The AP-1 complex heterotetramer μ subunit packages insulin receptor substrates into clathrin-coated vescicles. This is needed for insulin/insulin-like growth factor bioactivities including mitogenesis[2].
The AP-3 complex heterotetramer is involved in the biogenesis of lysosome-related organelles[3]. It contains subunits β3, μ3, δ and σ3[4].
The AP-4 complex heterotetramer is involved in the targeting proteins from the trans-Golgi network (TGN) to yhr endosomal-lysosomal system. It contains subunits β-type, μ-type, ε and σ-type[5].
3D structures of adaptin
Adaptin 3D structures
