Fig. 2: Equilibrium and kinetic tensiometry binding analysis reveal synergy between AP2 and cargo in binding PM monolayers. | Communications Biology

Fig. 2: Equilibrium and kinetic tensiometry binding analysis reveal synergy between AP2 and cargo in binding PM monolayers.

From: Combined thermodynamic and time-resolved structural analysis of interactions between AP2 and biomimetic plasma membranes provides insights into clathrin-mediated endocytosis

Fig. 2

A Increase in Surface Pressure (ΔΠ) as a function of time for different concentration of AP2 on lipid monolayers enriched in 10 wt. % PtdIns(4,5)P2 and TGN38 (2 wt. %). The initial surface pressure Π0 in all the cases has been fixed to 25 ± 1 mN/m similar to the lateral pressure in a plasma membrane leaflet. B Normalized surface pressure plotted against to the time elapsed after a lag period and fitted by a stretched exponential (straight lines) following Eq. 2. C Concentration dependence of the average relaxation ratio and a linear fit (straight lines). D Maximal increase in surface pressure ΔΠ∞ for lipid monolayers at different composition at Π0 = 25 ± 1 mN/m and a fixed concentration of AP2 of 500 nM. E Tensiometry binding analysis for AP2 recruited to a monolayer enriched in PtdIns(4,5)P2 and TGN38 or CD4 at different values of Π0. The increment in pressure, ΔΠ, is proportional to the amount of protein binding to the lipid monolayer at the air/water interface. Straight lines are fits to the experimental data obtained through the Hill-Langmuir relation (Eq. 1). F The increment in pressure, ΔΠ as a function of AP2 concentration for CD4 and TGN38 monolayers after subtracting PtdIns(4,5)P2 contribution. G Uppermost surface pressure increments due to the interaction of AP2 with a monolayer at Π0 = 25 ± 1 mN/m, at different concentration of PtdIns(4,5)P2. H Dissociation constants for PtdIns(4,5)P2 monolayers enriched in CD4 and TGN38 at different initial surface pressure. Bar diagrams in D,G,H are represented as mean ± S.D. (n = 5).

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