FIG. 1.
Binding of recombinant MoMuLV MA to LUVs measured by a cosedimentation assay. Pellets (P) and supernatants (SN) were migrated on gels and then transferred onto membranes and stained with Coomassie blue for visualization and quantification. (A) Images of the membranes corresponding to the binding of MoMuLV MA to PC/PS (60:40) (top), 95% PC/PI(4,5)P2 (95:5) (medium), and PC/PS/PI(4,5)P2 (75:20:5) (bottom panels). (B) The percentages of MA bound are represented at different acid lipid compositions. The x axis is the accessible (ACC) PI(4,5)P2 concentration. The curves are the least-square fits of equation 1 (see Materials and Methods), which yield the value for the molar partition coefficient, K, from which the affinity constant, Kd (Kd = 1/K), can be deduced. •, MuLV MA nonfitted values (PS). (C) Graph summarizing the Kd values obtained by repeating the same experiments for all the phosphoinositides {data represent means ± standard deviations obtained from at least two independent measurement [four for PI(4,5)P2]}. (D) Graph representing the variation in Kd calculated by comparing the Kd in the presence of PS (LUVs composed of PC/PS/PIP [75:20:5]) and in its absence (LUVs composed of PC/PIP [95:5]). Data were obtained in two independent experiments for PI(4,5)P2 and one experiment for the other phosphoinositides.