Lateral displacement of localized topological change in plasma membrane and the last granule position before fusion. (A, left) A dashed circle is centered on the last observed position of a fusing granule. (right) A solid circle is centered on the first observed location of a P/S spot. Bar, 800 nm. (B) The lateral displacement from the center of mass of the fusing granule to the center of mass of the P/S puncta for 23 fusion events is plotted in a frequency histogram. The mean displacement observed was 122 ± 15 nm.