Figure 2.

The BAF complex stabilizes actin filaments in the presence of PIP₂. (A) Polymerization of actin with no lipids added. HeLa or SW13 complexes were purified using BAF57 antibody; 5% pyrene-labeled actin was polymerized in the presence of either HeLa or SW13 complex at a concentration of ≈5 nM (as assessed by silver-stained gels) at 30°C. Polymerization is expressed by subtracting intrinsic fluorescence of pyrene-labeled G actin (as measured using 3 μM G actin), then calculating fluorescence as a percentage of final fluorescence of the SW13 sample. (B) As in A, except HeLa or SW13 complex was added to actin and buffer along with sonicated micelles of either PIP₂ or PIP at a concentration of 50 μM. (C) As in A, except HeLa or SW13 complex was added to actin in the presence of 50 μM sonicated vesicles of phosphatidylcholine. (D) As in A, except HeLa or SW13 complex was added to actin in the presence of 50 μM sonicated vesicles of phosphatidylcholine containing 10% PIP₂.