Disordered proteins follow diverse transition paths as they fold and bind to a partner

Disordered proteins often fold as they bind to a partner protein. Most methods to measure transition paths rely on monitoring a single distance, making it difficult to resolve complex pathways. Kim and Chung used fast three-color single-molecule Foster resonance energy transfer (FRET) to simultaneously probe distance changes between the two ends of an unfolded protein and between each end and a probe on the partner protein.