Woori Bae †, Mal-Gi Choi ‡, Changbong Hyeon *§, Yeon-Kyun Shin *‡∥, and Tae-Young Yoon *†
† National Creative Research Initiative Center for Single-Molecule Systems Biology and Department of Physics, KAIST, Daejeon 305-701, South Korea
‡ Biomedical Research Institute, Korea Institute of Science and Technology, Seoul 136-791, South Korea
§ Korea Institute for Advanced Study, Seoul 130-722, South Korea
∥Department of Biophysics, Biochemistry and Molecular Biology, Iowa State University, Ames, Iowa 50011, United States
*Correspondence to: Changbong Hyeon, Yeon-Kyun Shin, Tae-Young Yoon
Current single-molecule techniques do not permit the real-time observation of multiple proteins interacting closely with each other. We here report an approach enabling us to determine the single-molecule fluorescence resonance energy transfer (FRET) kinetics of multiple protein?protein interactions occurring far below the diffraction limit. We observe a strongly cooperative formation of multimeric soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes, which suggests that formation of the first SNARE complex triggers a cascade of SNARE complex formation.