Membrane Protein Stoichiometry Determined from the Step‐Wise Photobleaching of Dye‐Labelled Subunits

Body count.In a generally applicable approach, the number of subunits in fluorescently-labelled protein complexes has been determined by counting photobleaching steps from individual molecules (see figure). The distribution of steps in the pore-forming toxins α-haemolysin and leukocidin indicate seven subunits for α-hemolysin, and four LukF and four LukS subunits for leukocidin.