Pentapeptide repeats are a family of
sequence motifs found in multiple tandem copies in
protein molecules. Pentapeptide repeat proteins are found in all species, but they are found in many copies in cyanobacterial genomes. The repeats were first identified by Black and colleagues in the hglK protein. The later Bateman
et al. showed that a large family of related pentapeptide repeat proteins existed. The function of these repeats is uncertain in most proteins. However, in the MfpA protein a DNA gyrase inhibitor it has been suggested that the pentapeptide repeat structure mimics the structure of DNA. The repeats form a regular right handed four sided
beta helix structure known as the Rfr-fold.