Single-Cell Single-Molecule Pull-Down (sc-SiMPull) for Detection of Protein Complexes from Embryonic Lysates.

Mapping how proteins form complexes and change binding partners is central to understanding cell signaling. Bulk biochemistry can provide a summary of what complexes are present in a cell, but information about the diversity of individual protein complexes is lost. Here, we describe single-cell , single-molecule pull-down (sc-SiMPull), a TIRF microscopy-based coimmunoprecipitation method, to visualize thousands of individual proteins, their binding partners, and protein complex stoichiometry directly from single-cell lysate. By iterating sc-SiMPull over time, temporal dynamics of protein complexes in response to signaling can be constructed.