Quantitative single-molecule imaging of protein assembly in membranes

Accurate knowledge of the mechanisms of assembly of protein complexes is essential to understand their structure and control their function. Deep insight into these mechanisms requires information at the single-molecule level to unveil processes which would be masked by ensemble measurements. Here, we describe single-molecule imaging (SMI) as a powerful tool to provide a quantitative characterization of the assembly of protein complexes through the determination of their copy number (or stoichiometry). We focus on membrane protein complexes and describe experimental and analytical strategies for their stoichiometry characterization in both model and cellular membranes.