The Tetratricopeptide repeat (TPR) typically contains 34 amino acids and is found in a variety of organisms including bacteria, cyanobacteria, yeast, fungi, plants, and humans. It is present in a variety of proteins including those involved in chaperone, cell-cycle, transcription, and protein transport complexes. The number of TPR motifs varies among proteins. Those containing 5-6 tandem repeats generate a right-handed helical structure with an amphipathic channel that is thought to accommodate an alpha-helix of a target protein. It has been proposed that TPR proteins preferentially interact with WD-40 repeat proteins, but in many instances several TPR-proteins seem to aggregate to multi-protein complexes.