Lipid, as well as content mixing, is defective with Sly1∆ polar loop mutants. Parallel lipid (top) and content mixing (bottom) results are shown from the same sets of reactions. (A and B) The content mixing data in A and B are identical to Fig. 6, G and J, and are shown here to facilitate comparison with the lipid mixing data. All reactions contained 3% PEG and 100 nM each of Sec17 and Sec18, and ATP. Lipid mixing is reported as raw fluorescence counts in arbitrary units. As the membranes mix, FRET from Marina Blue DHPE to NBD-DHPE (initially in separate liposomes) quenches Marina Blue emission at 465 nm. Points and bars in all traces show means ± SEM of data from three separate experiments.