Structural and functional division into two domains of the large (100- to 115-kDa) chains of the clathrin-associated protein complex AP-2.

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Abstract
The clathrin-associated protein complex 2 (AP-2 complex) is a group of proteins associated with clathrin-coated vesicles and believed to interact with cytoplasmic domains of receptors found in the plasma membrane. AP-2 was purified as an assembly of several polypeptide chains (.alpha., .beta., AP50, and AP17), of which only the .alpha. and .beta. chains (100-115 kDa) show significant heterogeneity. We have obtained cDNA clones for two distinct rat brain .beta. chains. We have also studied the domain organization of bovine brain AP-2 complexes by selective proteolysis. Results of these studies show that the .alpha. and .beta. chains have a similar two-domain organization. Their amino-terminal domains are relatively invariant whereas their carboxyl-terminal domains are variable in both sequence and length. We propose that the variable domains select receptors for inclusion in coated vesicles.