title: Dissecting and reprogramming the folding and assembly of tandem-repeat proteins.
abstract: Studying protein folding and protein design in globular proteins presents significant challenges because of the two related features, topological complexity and co-operativity. In contrast, tandem-repeat proteins have regular and modular structures composed of linearly arrayed motifs. This means that the biophysics of even giant repeat proteins is highly amenable to dissection and to rational design. Here we discuss what has been learnt about the folding mechanisms of tandem-repeat proteins. The defining features that have emerged are: (i) accessibility of multiple distinct routes between denatured and native states, both at equilibrium and under kinetic conditions; (ii) different routes are favoured for folding compared with unfolding; (iii) unfolding energy barriers are broad, reflecting stepwise unravelling of an array repeat by repeat; (iv) highly co-operative unfolding at equilibrium and the potential for exceptionally high thermodynamic stabilities by introducing consensus residues; (v) under force, helical-repeat structures are very weak with non-co-operative unfolding leading to elasticity and buffering effects. This level of understanding should enable us to create repeat proteins with made-to-measure folding mechanisms, in which one can dial into the sequence the order of repeat folding, number of pathways taken, step size (co-operativity) and fine-structure of the kinetic energy barriers.
authors.affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
authors.forename: Pamela J E
authors.initials: PJ
authors.lastname: Rowling
authors.affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
authors.forename: Elin M
authors.initials: EM
authors.lastname: Sivertsson
authors.affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
authors.forename: Albert
authors.initials: A
authors.lastname: Perez-Riba
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, U.K. e.main@qmul.ac.uk lsi10@cam.ac.uk.
authors.forename: Ewan R G
authors.initials: ER
authors.lastname: Main
authors.affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K. e.main@qmul.ac.uk lsi10@cam.ac.uk.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Itzhaki
mesh_terms: D000818:Animals; D016384:Consensus Sequence; D004735:Energy Transfer; D006801:Humans; D008958:Models, Molecular; D008970:Molecular Weight; D011487:Protein Conformation; D015202:Protein Engineering; D017510:Protein Folding; D055503:Protein Multimerization; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D020080:Tandem Repeat Sequences
chemical_list: D011993:Recombinant Fusion Proteins
keywords: TPR; ankyrin; protein design; protein engineering; protein folding; tandem-repeat protein; tetratricopeptide