InterPro domain: IPR000261

The EH (for Eps15 Homology) domain is a protein-protein interaction module of approximately 95 residues which was originally identified as a repeated sequence present in three copies at the N terminus of the tyrosine kinase substrates Eps15 and Eps15R [ 1 , 2 ]. The EH domain was subsequently found in several proteins implicated in endocytosis, vesicle transport and signal transduction in organisms ranging from yeast to mammals. EH domains are present in one to three copies and they may include calcium-binding domains of the EF-hand type [ 3 , 4 ]. Eps15 is divided into three domains: domain I contains signatures of a regulatory domain, including a candidate tyrosine phosphorylation site and EF-hand-type calcium-binding domains, domain II presents the characteristic heptad repeats of coiled-coil rod-like proteins, and domain III displays a repeated aspartic acid-proline-phenylalanine motif similar to a consensus sequence of several methylases [ 5 ].

EH domains have been shown to bind specifically but with moderate affinity to peptides containing short, unmodified motifs through predominantly hydrophobic interactions. The target motifs are divided into three classes: class I consists of the concensus Asn-Pro-Phe (NPF) sequence; class II consists of aromatic and hydrophobic di- and tripeptide motifs, including the Phe-Trp (FW), Trp-Trp (WW), and Ser-Trp-Gly (SWG) motifs; and class III contains the His-(Thr/Ser)-Phe motif (HTF/HSF) [ 6 , 7 ]. The structure of several EH domains has been solved by NMR spectroscopy. The fold consists of two helix-loop-helix characteristic of EF-hand domains, connected by a short antiparallel beta-sheet. The target peptide is bound in a hydrophobic pocket between two alpha helices. Sequence analysis and structural data indicate that not all the EF-hands are capable of binding calcium because of substitutions of the calcium-liganding residues in the loop [ 8 , 9 , 10 ].

This domain is often implicated in the regulation of protein transport/sorting and membrane trafficking. Messenger RNA translation initiation and cytoplasmic poly(A) tail shortening require the poly(A)-binding protein (PAB) in yeast. The PAB-dependent poly(A) ribonuclease (PAN) is organised into distinct domains containing repeated sequence elements [ 11 ].

1. A protein-binding domain, EH, identified in the receptor tyrosine kinase substrate Eps15 and conserved in evolution. Proc. Natl. Acad. Sci. U.S.A. 92, 9530-4
2. The Eps15 homology (EH) domain. FEBS Lett. 513, 24-9
3. EH: a novel protein-protein interaction domain potentially involved in intracellular sorting. Trends Biochem. Sci. 22, 411-3
4. Endocytosis: EH domains lend a hand. Curr. Biol. 9, R70-3
5. eps15, a novel tyrosine kinase substrate, exhibits transforming activity. Mol. Cell. Biol. 13, 5814-28
6. Binding specificity and in vivo targets of the EH domain, a novel protein-protein interaction module. Genes Dev. 11, 2239-49
7. Recognition specificity of individual EH domains of mammals and yeast. EMBO J. 17, 6541-50
8. Structure and Asn-Pro-Phe binding pocket of the Eps15 homology domain. Science 281, 1357-60
9. Solution structure of Eps15's third EH domain reveals coincident Phe-Trp and Asn-Pro-Phe binding sites. Biochemistry 39, 4309-19
10. Solution structure of the Reps1 EH domain and characterization of its binding to NPF target sequences. Biochemistry 40, 6776-85
11. Translation initiation requires the PAB-dependent poly(A) ribonuclease in yeast. Cell 70, 961-73