title: Extension of the classical classification of β-turns.
abstract: The functional properties of a protein primarily depend on its three-dimensional (3D) structure. These properties have classically been assigned, visualized and analysed on the basis of protein secondary structures. The β-turn is the third most important secondary structure after helices and β-strands. β-turns have been classified according to the values of the dihedral angles φ and ψ of the central residue. Conventionally, eight different types of β-turns have been defined, whereas those that cannot be defined are classified as type IV β-turns. This classification remains the most widely used. Nonetheless, the miscellaneous type IV β-turns represent 1/3(rd) of β-turn residues. An unsupervised specific clustering approach was designed to search for recurrent new turns in the type IV category. The classical rules of β-turn type assignment were central to the approach. The four most frequently occurring clusters defined the new β-turn types. Unexpectedly, these types, designated IV1, IV2, IV3 and IV4, represent half of the type IV β-turns and occur more frequently than many of the previously established types. These types show convincing particularities, in terms of both structures and sequences that allow for the classical β-turn classification to be extended for the first time in 25 years.
authors.affiliation: INSERM, U 1134, DSIMB, F-75739 Paris, France.|Univ Paris Diderot, Sorbonne Paris Cité, UMR_S 1134, F-75739 Paris, France.|Institut National de la Transfusion Sanguine (INTS), F-75739 Paris, France.|Laboratoire d'Excellence GR-Ex, F-75739 Paris, France.
authors.forename: Alexandre G
authors.initials: AG
authors.lastname: de Brevern
mesh_terms: D000465:Algorithms; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000145:classification*
chemical_list: D011506:Proteins