Interaction of Two Structurally Distinct Sequence Types with the Clathrin Terminal Domain β-Propeller

The amino-terminal domain of the clathrin heavy chain, which folds into a seven-bladed β-propeller, binds directly to several endocytic proteins via short sequences based on the consensus residues LLDLD. In addition to a single LLDLD-based, type I clathrin-binding sequence, both amphiphysin and epsin contain a second, distinct sequence that is also capable of binding to clathrin directly. Here, we analyzed these sequences, which we term type II sequences, and show that the ²⁵⁷LMDLA sequence in rat epsin 1 appears to be a weak clathrin-binding variant of the sequence ⁴¹⁷PWDLW originally found in human amphiphysin II. The structural features of the type II sequence required for association with clathrin are distinct from the LLDLD-based sequence. In the central segment of amphiphysin, the type I and type II sequences cooperate to effect optimal clathrin binding and the formation of sedimentable assemblies. Together, the data provide evidence for two interaction surfaces upon certain endocytic accessory proteins that could cooperate with other coat components to enhance clathrin bud formation at the cell surface.