Membrane protein stoichiometry determined from the step-wise photobleaching of dye-labelled subunits.

10.1002/cbic.200600474

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Counting membrane protein stoichiometry.

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.