Common Evolutionary Origin of Swapped-Hairpin and Double-Psi β Barrels

• DOI: 10.1016/j.str.2006.08.005
• Publication Date: 2006-10-11T11:38:46Z
• Authors: Murray Coles; Michael Hulko; Sergej Djuranovic; Vincent Truffault; Kristin Koretke; Jörg Martin; Andrei N. Lupas
• Keywords: Models, Molecular; Protein Folding; 0303 health sciences; Molecular Sequence Data; Protein Structure, Secondary; Protein Structure, Tertiary; 03 medical and health sciences; Bacterial Proteins; Structural Biology; Amino Acid Sequence; Pyrococcus horikoshii; Molecular Biology; Dimerization

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.