On the origin and evolution of vertebrate and viral profilins

The three dimensional structures of profilins from invertebrates and vertebrates are remarkably similar despite low sequence similarity. Their evolutionary relationship remains thus enigmatic. A phylogenetic analysis of profilins from Deuterostoma indicates that profilin III and IV isoforms each form distinct groups. Profilin IV is most related to invertebrate profilins and originated prior to vertebrate evolution whereas separation of profilin I, II and III isoforms occurred early in vertebrate evolution. Viral profilins are most similar to profilin III. In silico analysis of representative profilin gene structures corroborates the phylogenetic result and we discuss this in terms of biochemical differences.