α-Helical coiled coils and bundles: How to design an α-helical protein

The presence of a periodic disposition of apolar residues at positions a and d within a heptad repeat (of the form (a b c d e f g) sub(n) super(10)), signals the potential for the interlocking of groups of alpha -helices. This type of periodicity is common in fibrous proteins, is characteristic of most membrane proteins, and is found as well in a wide range of globular proteins. Here the structures of these three protein classes are related more closely and special features of design are noted.