Amphilic structure

One of the most conspicuous features of residue distributions in membrane proteins is an aromatic belt, which sandwiches the apolar transmembrane domain. When aromatic residues are specifically displayed in membrane protein structures, a clustering in the interfacial region is often quite obvious. One example is shown in Fig. 3 (see color insert). Umschneider and Samsom (2001) have noted that this irregular distribution is restricted to Trp, His, and Tyr side chains, with Phe showing little preference for its location in the membrane. Thus, it appears that aromaticity and amphilicity are the preferred features. This aromatic belt reflects the favorable partitioning of aromatic amino acids into the interfacial region (Wimley and White, 1996 Yau et al., 1998) and may act to stabilize the orientation of the entire membrane protein or individual helices in the bilayer. 

Fujii, G. To fuse or not to fuse the effect of electrostatic interactions, hydrophobic forces and structural amphilicity on protein-mediated membrane destabilization. Adv. Drug Deliv. Rew. 1999, 38, 257-277. 

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