Identification of a conserved protein motif in a group of growth factor receptors

Residues 370-383 (helix C) of the human nerve growth factor receptor (NGF-R) are highly similar to the sequence of the 14 residue wasp toxin, mastoparan. Both regions are predicted to form amphiphilic alpha-helices, as is the amino-terminal region of the third intracytoplasmic loop (i3) of the beta 2-adrenergic receptor (beta 2AR). As both mastoparan and the beta 2AR i3 interact with G-proteins, it is suggested that helix C of the NGF-R may facilitate interactions with a cytoplasmic protein. A similar structural motif was identified in the cytoplasmic domains of a number of other growth factor receptors, suggesting an important role for this motif in signal transduction mechanisms.