Transient misfolding dominates multidomain protein folding

• DOI: 10.1038/ncomms9861
• Publication Date: 2015-11-17T10:42:40Z
• Authors: Alessandro Borgia; Katherine R. Kemplen; Madeleine B. Borgia; Andrea Soranno; Sarah Shammas; Bengt Wunderlich; Daniel Nettels; Robert B. Best; Jane Clarke; Benjamin Schuler
• Keywords: Repetitive Sequences, Amino Acid; 0301 basic medicine; Amyloid; Protein Folding; Microfluidics; General Physics and Astronomy; 610 Medicine & health; 1600 General Chemistry; General Chemistry; Molecular Dynamics Simulation; 3100 General Physics and Astronomy; Article; General Biochemistry, Genetics and Molecular Biology; Protein Structure, Tertiary; Kinetics; 03 medical and health sciences; 1300 General Biochemistry, Genetics and Molecular Biology; 10019 Department of Biochemistry; Fluorescence Resonance Energy Transfer; 570 Life sciences; biology; Humans; Connectin; Protein Unfolding

AbstractNeighbouring 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.