Transient misfolding dominates multidomain protein folding.

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Borgia, Alessandro 
Kemplen, Katherine R 
Borgia, Madeleine B 
Soranno, Andrea 
Shammas, Sarah 

Neighbouring domains of multidomain proteins with homologous tandem repeats have divergent sequences, probably as a result of evolutionary pressure to avoid misfolding and aggregation, particularly at the high cellular protein concentrations. Here we combine microfluidic-mixing single-molecule kinetics, ensemble experiments and molecular simulations to investigate how misfolding between the immunoglobulin-like domains of titin is prevented. Surprisingly, we find that during refolding of tandem repeats, independent of sequence identity, more than half of all molecules transiently form a wide range of misfolded conformations. Simulations suggest that a large fraction of these misfolds resemble an intramolecular amyloid-like state reported in computational studies. However, for naturally occurring neighbours with low sequence identity, these transient misfolds disappear much more rapidly than for identical neighbours. We thus propose that evolutionary sequence divergence between domains is required to suppress the population of long-lived, potentially harmful misfolded states, whereas large populations of transient misfolded states appear to be tolerated.

Amyloid, Connectin, Fluorescence Resonance Energy Transfer, Humans, Kinetics, Microfluidics, Molecular Dynamics Simulation, Protein Folding, Protein Structure, Tertiary, Protein Unfolding, Repetitive Sequences, Amino Acid
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Nat Commun
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Springer Science and Business Media LLC
Wellcome Trust (095195/Z/10/Z)
B.S. was supported by the Swiss National Science Foundation and the European Research Council. R.B. was supported by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney diseases of the National Institutes of Health. This study utilized the high-performance computational capabilities of the Biowulf Linux cluster at the National Institutes of Health, Bethesda, Md. ( This work was supported by the Wellcome Trust (WT095195) (J.C, S.L.S.), and an Engineering and Physical Sciences Research Council (UK) studentship (K.R.K.). J.C. is a Wellcome Trust Senior Research fellow.