where H represents hydrophobic residues, C represents, typically, charged residues, and P represents polar (and, therefore, hydrophilic) residues. The positions of the heptad repeat are commonly denoted by the lowercase letters a through g.
These motifs are the basis for most coiled coils and, in particular, leucine zippers, which have predominantly leucine in the d position of the heptad repeat.[2]
A conformational change in a heptad repeat in the SARS-CoV-2spike protein facilitates entry of the virus into the host cell membrane.[3]
^Seroski, Dillon T.; Hudalla, Gregory A. (2018). "Self-Assembled Peptide and Protein Nanofibers for Biomedical Applications". Biomedical Applications of Functionalized Nanomaterials. pp. 569–598. doi:10.1016/B978-0-323-50878-0.00019-7. ISBN978-0-323-50878-0.
