The heptad repeat is an example of a
structural motif that consists of a repeating pattern of seven
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
s:
''a b c d e f g''
H P P H C P C
where H represents
hydrophobic
In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water.
Hydrophobic molecules tend to be nonpolar and, thu ...
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 zipper
A leucine zipper (or leucine scissors) is a common three-dimensional structural motif in proteins. They were first described by Landschulz and collaborators in 1988 when they found that an enhancer binding protein had a very characteristic 30-amin ...
s, which have predominantly
leucine in the ''d'' position of the heptad repeat.
A conformational change in a heptad repeat in the
SARS-CoV-2
Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19, the respiratory illness responsible for the COVID-19 pandemic. The virus previously had the Novel coronavirus, provisional nam ...
spike protein
In virology, a spike protein or peplomer protein is a protein that forms a large structure known as a spike or peplomer projecting from the surface of an viral envelope, enveloped virus. as cited in The proteins are usually glycoproteins that ...
facilitates entry of the virus into the host cell membrane.
References
{{DEFAULTSORT:Heptad Repeat
Protein structural motifs