Amphipathic Alpha Helix

**Semantic type:** Spatial Concept

**Definition:** The amphipathic helix motif is characterized by a repeating pattern of polar (P) and non-polar (N) side-chains that can be summarized as PxNPPNx. These clusters varied in length from 6 to 15 residues. The conserved non-polar positions are marked by a distinct absence of Asp, Asn and Ser, while other polar side chains are sometimes allowed.