Figure 1.
F-actin localizes to the periphery of polypeptide coacervates. (A and B) Confocal fluorescence (left and middle) and DIC (right) micrographs are shown of polypeptide coacervates containing both TMR-actin (green) and 647-BSA (orange) on nonadherent substrates. (A and B) Focal plane is at the interface of the coacervates and the substrate (surface (A)), or near the midplane of the largest droplet (B), indicated by the dashed yellow line in (C). (C) An x-z cross section is formed from the intensity values along the dashed lines in (B) evaluated in all planes of a confocal z-stack. Scale bar, 5 μm in (A–C). (D) Normalized intensity line scans are given along the dashed yellow lines as indicated in (B) and (C). (E) Average RAM is given for coacervates in samples containing 0.5 μM actin alone, 0.5 μM BSA alone, or 0.25 μM actin and 0.25 μM BSA together (A–D). Error bars denote standard error of the mean. The number of droplets included in each condition is listed on the bar. Conditions are 0.5 μM total protein (0.25 μM Mg-ATP-actin (47% TMR-labeled) and 0.25 μM BSA (91% Alexa-647-labeled)) incubated with 5 mM pLK before addition of 5 mM pRE in 50 mM KCl, 1 mM MgCl2, 1 mM EGTA, 10 mM imidazole (pH 7.0), and 72 μM ATP (all concentrations final). To see this figure in color, go online.