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.
Pubmed ID: 9034331 RIS Download
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Software package of molecular simulation programs. It is distributed into AmberTools15 and Amber14. AmberTools15 is a software package which can carry out complete molecular dynamics simulations with either explicit water or generalized Born solvent models. It is distributed in source code format and must be compiled in order to be used. Amber14 builds on AmberTools15 by adding the pmemd program, which provides better performance on multiple CPUs and dramatic speed improvements on GPUs compared to sander (molecular dynamics). GPU info, manuals, and tutorials are available on the website.
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