title: The folding pathway of an engineered circularly permuted PDZ domain.
abstract: To understand the role of sequence connectivity in the folding pathway of a multi-state protein, we have analysed the folding kinetics of an engineered circularly permuted PDZ domain. This variant has been designed with the specific aim of posing two of the strands participating in the stabilisation of an early folding nucleus as contiguous elements in the primary structure. Folding of the circularly permuted PDZ2 has been explored by a variety of different experimental approaches including stopped-flow and continuous-flow kinetics, as well as ligand-induced folding experiments. Data reveal that although circular permutation introduces a significant destabilisation of the native state, a folding intermediate is stabilised and accumulated prior folding. Furthermore, quantitative analysis of the observed kinetics indicates an acceleration of the early folding events by more than two orders of magnitude. The results support the importance of sequence connectivity both in the mechanism and the speed of protein folding.
authors.affiliation: Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Sapienza - Università di Roma, Piazzale A., Rome, Italy.
authors.forename: Ylva
authors.initials: Y
authors.lastname: Ivarsson
authors.forename: Carlo
authors.initials: C
authors.lastname: Travaglini-Allocatelli
authors.forename: Veronica
authors.initials: V
authors.lastname: Morea
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brunori
authors.forename: Stefano
authors.initials: S
authors.lastname: Gianni
mesh_terms: D002942:Circular Dichroism; D007700:Kinetics; D008958:Models, Molecular; D054731:PDZ Domains; D011487:Protein Conformation; D015202:Protein Engineering; D017510:Protein Folding