Figure 6

PI(4,5)-P₂ inefficiently competes with actin for binding to R136D profilin I. The curves shown are : 8 μM Mg²⁺-ATP-G-α-actin (5% pyrene labeled) alone (closed triangles) or with 4 μM wild type profilin I (closed circles), 4 μM R136D (open circles), 4 μM wild type profilin I and 36 μM PI(4,5)-P₂ (closed squares), 4 μM R136D and 36 μM PI(4,5)-P₂ (open squares).