Small tetracysteine insertions are more suitable for fl uorescence resonance energy transfer (FRET) studies of protein folding and small complex assembly than bulky GFP-based fl uorophores. Here, we describe a procedure for expression, purifi cation, and fl uorescent labeling of a FRET-based probe, called CSNAC that can track the conformational changes undergone by SNAP-25 as it folds in the exocytic complex. The fl uorescent protein Cerulean was attached to the N-terminus and served as a FRET donor. The biarsenical dye FlAsH, served as a FRET acceptor, was bound to a short tetracysteine motif positioned in the linker domain of SNAP-25. CSNAC can report real-time FRET changes when the Syntaxin soluble domain is added in vitro.
ASJC Scopus subject areas
- Molecular Biology