alpha Adaptin [100/2]

100/2

AP2 polypeptides from bovine brain.

alpha Adaptin

0. 1% Sodium Azide; Constituents: Ascites fluid

Cytoplasmic In eukaryotic cells clathrin-coated vesicles mediate the selective internalization of cell-surface receptors for lysosomal enzymes from the trans-Golgi network to a pre-lysosomal compartment. Besides clathrin coated vesicle populations contain the adaptor complexes AP1 and AP2 also known as HAI (HA1) adaptor and HAII (HA2) adaptor or Assemble Protein 1 (AP1) and Assemble Protein 2 (AP2) respectively. Interest has focused on adaptors because they are known to mediate the interaction between clathrin and components of the membrane. Their location between the clathrin shell and the membrane as revealed by cryoelectron microscopy is consistent with such a function. Under physiological conditions in vitro adaptory proteins readily bind to clathrin and thereby induce its polymerization into regular polyhedral coat structures very similar to the coats of coated vesicles. Clathrin-coated membranes at or originating from the plasma membrane contain the AP2 adaptor while the AP1 adaptor appears to be largely restricted to clathrin-coated membranes of the trans-Golgi network. Both the Golgi associated AP1 adaptor and the plasma-membrane associated AP2 adaptor are heterotetrameric protein complexes. AP2 adaptor is made up of two 100-110 kD polypeptides termed alpha and beta 2 (formerly beta) subunits F2 (50 kD) and omega 2 (17 kD) subunit. alpha and beta 2 subunits (alpha and beta 2 adaptins) behave in standard SDS-PAGE like 100-112 kD polypeptides. Four alpha isoforms (alpha a1 alpha a2 alpha c1 and alpha c2) which are highly homologous in sequence have been described. beta 1 and beta 2 adaptins are highly homologous which suggests that the beta type adaptor chains may mediate the interaction of their adaptors with the highly conserved clathrin molecule. The alpha and gamma adaptins share only 25% overall identity. The other adaptor subunits of the two adaptor complexes which appear to be unrelated are believed to possess binding sites for different cargo molecules (receptors) and for proteins which might regulate the complex functions of the adaptors. Monoclonal antibodies reacting specifically against adaptor proteins are useful tools for studies on the intracellular distribution and structural relationship of adaptor complexes.

Adaptor protein complex 2 (AP-2) is an heterotetramer composed of two large adaptins (alpha-type subunit AP2A1 or AP2A2 and beta-type subunit AP2B1) a medium adaptin (mu-type subunit AP2M1) and a small adaptin (sigma-type subunit AP2S1). Component of a complex composed at least of ACTB AP2M1 AP2A1 AP2A2 MEGF10 and VIM. Interacts with RAB11FIP2 (By similarity).

Isoform A is expressed only in neuronal tissue and skeletal muscle. Isoform B is widely expressed.