Probing the extended lipid anchorage with cytochrome c and liposomes containing diacylphosphatidylglycerol lipids

Experiments investigating the adsorption and desorption of cytochrome c onto and from liposomes containing 50 mol% 1,2-diacylphosphatidylglycerol lipids 10:0, 12:0, 14:0, 16:0, 18:1(Δ9 cis)] with 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) in pH 7.4 buffered solutions of low to moderate ionic strength are reported. Fluorescence experiments show that cytochrome c has a similar adsorption affinity for the five labeled 50 mol% PG liposome systems investigated. Fluorescence recovery experiments reveal the extent of cytochrome c desorption upon the addition of >10× excess of unlabeled 100% 1,2-dioleoyl-sn-glycero-3-phosphatidylglycerol (DOPG) liposomes is dependent on the lipid's acyl chain length. The extent of desorption is also shown to be independent of temperature, albeit over a narrow range. The differences in the extent of cytochrome c desorption from liposomes containing PG lipids with different acyl chain lengths is attributed to the varying contribution of the binding motif involving the extended lipid anchorage in response to lipid packing stress.