Eps15 homology (EH) domains are protein interaction modules that recognize
Asn-Pro-Phe (NPF) motifs in their biological ligands to mediate critical events
during endocytosis and signal transduction. To elucidate the structural basis
of the EH−NPF interaction, the solution structures of two EH−NPF
complexes were solved using NMR spectroscopy. The first complex contains a
peptide representing the Hrb C-terminal NPFL motif; the second contains a
peptide in which an Arg residue substitutes the C-terminal Leu. The NPF residues
are almost completely embedded in a hydrophobic pocket on the EH domain surface
and the backbone of NPFX adopts a conformation reminiscent of the Asx-Pro
type I -turn motif. The residue directly following NPF is crucial for
recognition and is required to complete the -turn. Five amino acids
on the EH surface mediate specific recognition of this residue through hydrophobic
and electrostatic contacts. The complexes explain the selectivity of the second
EH domain of Eps15 for NPF over DPF motifs and reveal a critical aromatic
interaction that provides a conserved anchor for the recognition of FW, WW,
SWG and HTF ligands by other EH domains.
-turn motif. The residue directly following NPF is crucial for
recognition and is required to complete the 
