Identification of two new mu-adaptin-related proteins, mu-ARP1 and mu-ARP2

We report the cDNA cloning, primary structure and tissue distribution of two new proteins homologous to mu-adaptins, the medium chains of the clathrin coat adaptor complexes, Both predicted proteins share 60% amino acid sequence identity with each other and 27-31% identity with mu 1-adaptin (ap47) and mu 2-adaptin (ap50), Lower similarity (23-25% identity) is found with two other mu-adaptin-related proteins, p47A/B, and there is similarity over the N-terminal 150 amino acids with the adaptin small chains and delta-COP. The mRNAs of both molecules are expressed in all tissues analyzed, but with different profiles of relative abundance, mu-ARP1 is most abundant in brain, ovary and lung, whereas mu-ARP2 is prominently expressed in testis, These proteins suggest the existence of as Set uncharacterized types of clathrin- or non-clathrin-associated protein coats in cellular membrane traffic, of which they are probably prototype subunits, and provide molecular markers and probes for their characterization.