Amphipathic helices with heptad repeats
Each strand of a coiled-coil protein
consists of repeated consensus sub-
strings of the form (a-b-c-d-e-f-g)n,
where a, b, c,...,g are seven different
structural positions on the coil.
The first and fourth position (a and d)
are hydrophobic amino acids. When
the two strands coil around each other
positions a and d are internalized,
stabilizing the structure, while
positions b, c, e, f, g are exposed
on the surface of the protein.