Structure/function analysis of the interaction of phosphatidylinositol 4,5-bisphosphate with actin-capping protein: Implications for how capping protein binds the actin filament

Kyoungtae Kim, Michelle E. McCully, Nandini Bhattacharya, Boyd Butler, David Sept, John A. Cooper

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

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.

Original languageEnglish
Pages (from-to)5871-5879
Number of pages9
JournalJournal of Biological Chemistry
Volume282
Issue number8
DOIs
StatePublished - Feb 23 2007

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