Adaptor Related Protein Complex 3 Sigma 2 (AP3s2)

Clathrin-associated adaptor complexes are cytoplasmic protein coats that play a role in general transport and sorting processes. The smallest component of AP3 was determined to be either sigma-3A (AP3S1) or sigma-3B.Sigma-3B was cloned by homology with rat and mouse sigma components from previously characterized adaptor complexes, AP1 and AP2. An extended C-terminal segment of sigma-3 was necessary for the interaction with the delta subunit. The delta-sigma-3 interaction interfered with the binding of AP3 to ARF, but not with its binding to dileucine-based sorting signals. As a consequence, the delta subunit ear inhibited the recruitment of AP3 to membranes both in vitro and in vivo and impaired the sorting of lysosomal membrane proteins.