title: Common evolutionary origin of swapped-hairpin and double-psi beta barrels.
abstract: The core of swapped-hairpin and double-psi beta barrels is formed by duplication of a conserved betaalphabeta element, suggesting a common evolutionary origin. The path connecting the two folds is unclear as the two barrels are not interconvertible by a simple topological modification, such as circular permutation. We have identified a protein family whose sequence properties are intermediate to the two folds. The structure of one of these proteins, Pyrococcus horikoshii PhS018, is also built by duplication of the conserved betaalphabeta element but shows yet a third topology, which we name the RIFT barrel. This topology is widespread in the structure database and spans three folds of the SCOP classification, including the middle domain of EF-Tu and the N domain of F1-ATPase. We propose that swapped-hairpin beta barrels arose from an ancestral RIFT barrel by strand invasion and double-psi beta barrels by a strand swap. We group the three barrel types into a metafold, the cradle-loop barrels.
authors.affiliation: Department of Protein Evolution, Max-Planck-Institute for Developmental Biology, 72076 Tübingen, Germany.
authors.forename: Murray
authors.initials: M
authors.lastname: Coles
authors.forename: Michael
authors.initials: M
authors.lastname: Hulko
authors.forename: Sergej
authors.initials: S
authors.lastname: Djuranovic
authors.forename: Vincent
authors.initials: V
authors.lastname: Truffault
authors.forename: Kristin
authors.initials: K
authors.lastname: Koretke
authors.forename: Jörg
authors.initials: J
authors.lastname: Martin
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Lupas
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D043902:Pyrococcus horikoshii / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins