A protein complex associated with coated vesicles. Adaptors have been shown to promote the in vitro assembly of clathrin cages and to bind to the cytoplasmic domains of specific membrane proteins. It has been proposed that adaptors link selected membrane proteins to clathrin causing them to be packaged into a coated vesicle. Two adaptors have been identified (HA-1 and HA-2) ; they are hetero-tetramers composed of two proteins of 100-110 kD, termed adaptins, and two smaller polypeptides of around 50 and 20 kD. The HA-1 subunits are g -adaptin, b \'-adaptin with polypeptides of 50 kD and 17 kD. HA-1 is associated with coated pits formed from the Golgi complex. The HA-2 subunits are a -adaptin, b -adaptin with polypeptides of 47 kD and 20 kD. HA-2 is associated with coated pits formed from the plasma membrane. ( b &’- and b -adaptin are closely related).
Dictionary of molecular biology. 2004.