Structure/function analysis of the interaction of phosphatidylinositol 4,5-bisphosphate with actin-capping protein: Implications for how capping protein binds the actin filament
The heterodimeric actin-capping protein (CP) can be inhibited by polyphosphoinositides, which may be important for actin polymerization at membranes in cells. Here, we have identified a conserved set of basic residues on the surface of CP that are important for the interaction with phosphatidylinositol 4,5-bisphosphate (PIP2). Computational docking studies predicted the identity of residues involved in this interaction, and functional and physical assays with site-directed mutants of CP confirmed the prediction. The PIP2 binding site overlaps with the more important of the two known actin-binding sites of CP. Correspondingly, we observed that loss of PIP2 binding correlated with loss of actin binding among the mutants. Using TIRF (total internal reflection fluorescence) microscopy, we observed that PIP2 rapidly converted capped actin filaments to a growing state, consistent with uncapping. Together, these results extend our understanding of how CP binds to the barbed end of the actin filament, and they support the idea that CP can "wobble" when bound to the barbed end solely by the C-terminal "tentacle" of its β-subunit. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc.
This research was originally published in the Journal of Biological Chemistry 282, no. 8 (2007): 5871-5879. © 2007 the American Society for Biochemistry and Molecular Biology
Kim, Kyoungtae, Michelle E. McCully, Nandini Bhattacharya, Boyd Butler, David Sept, and John A. Cooper. "Structure/function analysis of the interaction of phosphatidylinositol 4, 5-bisphosphate with actin-capping protein: implications for how capping protein binds the actin filament." Journal of Biological Chemistry 282, no. 8 (2007): 5871-5879.
Journal of Biological Chemistry