Figure 7.

Calculation of the saturation dependence of filament elongation by Ena/VASP proteins. Comparison of the calculated elongation rates for processive filament elongation mediated by hVASP WT and hVASP DdGAB over a large range of actin concentrations. Grey boxes indicate G-actin concentrations typically used in TIRF assays or present in biomimetic motility assays (Samarin et al, 2003), as well as physiological G-actin concentrations, for instance in the lamellipodium tip (Koestler et al, 2009). Different G-actin affinities of the GAB motifs result in markedly different elongation rates mediated by chimeras hVASP and hVASP DdGAB in TIRF assays. However, both proteins are expected to be saturated with actin monomers and to enhance filament elongation to the same extent at very high monomer concentrations, for example under in vivo conditions.