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The mammalian profilin isoforms display complementary affinities for PIP2 and proline‐rich sequences

Anja Lambrechts, Jean‐Luc Verschelde, Veronique Jonckheere, Mark Goethals, Joël Vandekerckhove, Christophe Ampe

Author Affiliations

  1. BIO FROM CONTRIB-GROUP Anja Lambrechts1,
  2. BIO FROM CONTRIB-GROUP Jean‐Luc Verschelde1,
  3. BIO FROM CONTRIB-GROUP Veronique Jonckheere1,
  4. BIO FROM CONTRIB-GROUP Mark Goethals1,
  5. BIO FROM CONTRIB-GROUP Joël Vandekerckhove1 and
  6. BIO FROM CONTRIB-GROUP Christophe Ampe1
  1. 1 Flanders Interuniversity Institute for Biotechnology, Department of Biochemistry, Faculty of Medicine, Universiteit Gent, 9000, Gent, Belgium

Abstract

We present a study on the binding properties of the bovine profilin isoforms to both phosphatidylinositol 4,5‐bisphosphate (PIP2) and proline‐rich peptides derived from vasodilator‐stimulated phosphoprotein (VASP) and cyclase‐associated protein (CAP). Using microfiltration, we show that compared with profilin II, profilin I has a higher affinity for PIP2. On the other hand, fluorescence spectroscopy reveals that proline‐rich peptides bind better to profilin II. At micromolar concentrations, profilin II dimerizes upon binding to proline‐rich peptides. Circular dichroism measurements of profilin II reveal a significant conformational change in this protein upon binding of the peptide. We show further that PIP2 effectively competes for binding of profilin I to poly‐l‐proline, since this isoform, but not profilin II, can be eluted from a poly‐l‐proline column with PIP2. Using affinity chromatography on either profilin isoform, we identified profilin II as the preferred ligand for VASP in bovine brain extracts. The complementary affinities of the profilin isoforms for PIP2 and the proline‐rich peptides offer the cell an opportunity to direct actin assembly at different subcellular localizations through the same or different signal transduction pathways.

  • Received June 20, 1996.
  • Revision received October 10, 1996.