TABLE II.
Examples of Actin-Binding Proteins in Platelets
| Type of Activity | Concentration | Cofactors |
|---|---|---|
| Monomer-binding proteins | ||
| Profilin | 0.5 μM | Binds polyproline repeats, inhibited by PIP2 |
| Thymosin β4 | 500 μM | |
| Depolymerizing factors | ||
| Cofilin/ADF | 50 μM | Activated by dephosphorylation, inactivated by phosphorylation by LIM kinase |
| Barbed-end capping proteins | ||
| Gelsolin | 12 μM | Calcium, PIP2 |
| Capping protein | 2–5 μM | PIP2 |
| gCap 39 | 5 μM | |
| Side-binding proteins | ||
| VASP | 5 μM | Phosphorylation by cGMP/cAMP kinases |
| Actin-binding protein | Proteolysis | |
| Spectrin | Proteolysis | |
| Nucleator | ||
| Arp2/3 | ND | N-WASp/Scar |
| Kaptin (2E4) | ND |