EPR Lineshape Analysis to Investigate the SNARE Folding Intermediates.

SNARE complex formation, which is believed to drive intracellular membrane fusion, transits through multiple conformational states along the membrane fusion pathway. The SNARE intermediates are biologically important because they serve as targets for fusion regulators and clostridial neurotoxins. Spin-labeling EPR has contributed significantly to the understanding of the structures and the dynamics of SNARE intermediates. In particular, the EPR lineshape analysis, which is highly sensitive to protein conformational changes such as the local coil-to-helix transition, has revealed the sequential compacting steps leading to formation of the highly stable four-helix bundle.