This is a designed protein. There are 3 parallel helices, of slightly different sequences. The interface is mostly Ile, colored yellow. There is a single Leu, colored red. Note: the coiled-coil is left-handed.

Nautiyal, S., Alber, T. C.: Crystal Structure of a Designed, Thermostable, Heterotrimeric Coiled Coil Protein Sci. 8 pp. 84 (1999)(PubMed)

1bb1 (PDB)