The EH1 domain of Eps15 is structurally classified as a member of the S100subclass of EF-hand-containing proteins

The Eps15 homology (EH) domain is a protein-protein interaction module that binds to proteins containing the asparagine-proline-phenylalanine (NPF) or tryptophan/phenylalanine-tryptophan (W/FW) motif. EH domain-containing pro teins serve important roles in signaling and processes connected to transpo rt, protein sorting, and organization of subcellular structure. Here, we re port the solution structure of the apo form of the EH1 domain of mouse Eps1 5, as determined by high-resolution multidimensional heteronuclear NMR spec troscopy. The polypeptide folds into six alpha-helices and a short antipara llel beta-sheet, Additionally, it contains a long, structured, topologicall y unique C-terninal loop. Helices 2-5 form two EF-hand motifs. Structural s imilarity and Ca2+ binding properties lead to classification of the EH1 dom ain as a member of the S100 subclass of EF-hand-containing proteins, albeit with a unique set of interhelical angles. Binding studies using an eight-r esidue NPF-containing peptide derived from RAB, the cellular cofactor of th e HIV Rev protein, show a hydrophobic peptide-binding pocket formed by cons erved tryptophan and leucine residues.