Profilins (PFNs) are a group of small eukaryotic proteins that bind to monomeric actin (G-actin) in a 1:1 ratio thus preventing the polymerisation of actin into filaments (F-actin). They can also in certain circumstance promote actin polymerisation. Profilins also bind to polyphosphoinositides such as PIP2 []. Other ligands include members of the Ena/VASP and formin families []. Overall sequence similarity among profilin from organisms which belong to different phyla (ranging from fungi to mammals) is low, but the N-terminal region is relatively well conserved. The N-terminal region is thought to be involved in actin binding. Four Profilins have been identified in mammals, PFN1-4. PFN1 and PFN2 differentially regulate membrane protrusion, motility, and invasion; these processes are promoted by PFN1 and suppressed by PFN2 []. This entry represents PFN1.
