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.
- ankyrin
- protein design
- protein engineering
- protein folding
- tandem-repeat protein
- tetratricopeptide
- TPR
Footnotes
Repetitive, Non-Globular Proteins: Nature to Nanotechnology: Held at the University of York, U.K., 30 March 2015–1 April 2015.
Abbreviations
- ANK,
- ankyrin repeat;
- CTPRa,
- consensus TPR;
- TPR,
- tetratricopeptide repeat
- © 2015 Authors; published by Portland Press Limited