Once activated by binding to GTP-bound CDC42, FMNL2 interacts with actin bound profilin(s) and drives elongation but not nucleation of actin filaments (Block et al. 2012). The interaction between formins and profilins is achieved through the proline-rich FH1 domain of formins, while the interaction with actin is achieved through the FH2 domain of formins (Romero et al. 2004, Kovar et al. 2006, Kuhn and Geyer 2014).