Heptad repeat

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The heptad repeat is an example of a structural motif that consists of a repeating pattern of seven amino acids:[1]

 a b c d e f g
 H P P H C P C

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-2 spike protein facilitates entry of the virus into the host cell membrane.[3]


  1. ^ 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. ISBN 978-0-323-50878-0.
  2. ^ Chambers P, Pringle CR, Easton AJ (1990). "Heptad repeat sequences are located adjacent to hydrophobic regions in several types of virus fusion glycoproteins". The Journal of General Virology. 71 (12): 3075–80. doi:10.1099/0022-1317-71-12-3075. PMID 2177097.
  3. ^ Jackson CB, Farzan M, Chen B, Choe H (2022). "Mechanisms of SARS-CoV-2 entry into cells". Nature Reviews Molecular Cell Biology. 23 (1): 3–20. doi:10.1038/s41580-021-00418-x. PMC 8491763. PMID 34611326.