Binds to actin and affects the structure of the cytoskeleton. At high concentrations, profilin prevents the polymerization of actin, whereas it enhances it at low concentrations (By similarity). Has a high affinity for poly-proline (PubMed:20484919). Occurs in many kinds of cells as a complex with monomeric actin in a 1:1 ratio. Causes an allergic reaction in human (PubMed:20484919, PubMed:19295232, PubMed:12642849). Binds to IgE of patients allergic to melon (Cucumis melo) (PubMed:12642849). Binds to IgE of patients with oral allergy symptoms and pollen allergy to watermelon (PubMed:20484919, PubMed:19295232). Binds to IgE in 100% of the 17 patients tested (PubMed:20484919). Binds to IgE in 56% of the 23 patients tested. IgE-binding is lost by digestion with pepsin (PubMed:19295232). Induces degranulation of human basophils (PubMed:20484919). Belongs to the profilin family.