Fig. 1. EHD1 domain organization and homology to GTP-binding proteins. A schematic representation of human EHD1. EHD1 comprises an N-terminal P-loop, a central coiled coil and a C-terminal EH domain. EHD1 motifs that conform to polypeptide loops involved in GTP binding are shown at amino acids 65–72 (G1) and 217–222 (G4). Note that G2 and G5 motifs (which are more heterogeneous) have not been identified in EHD1, and a sequence with low homology to the G3 motif consensus is found between amino acids 351 and 358 (data not shown). The G1 and G4 amino acid sequences of EHD1 are aligned with those of the GTP-binding protein H-Ras, and with a consensus sequence for Ras-family GTP-binding motifs. X represents any amino acid; Φ represents a bulky hydrophobic amino acid.