Actin is one of the most abundant intracellular proteins and it is highly conserved across all eukaryotes. The primary functional form of actin is the filament, formed by the polymerization of actin monomers. This polymerization process is exquisitely controlled through a host of actin-binding proteins, but since actin is an ATPase, it is also a function of the bound nucleotide. Much of our understanding of actin comes from experiments using animal cells, but even though the protein sequence is strongly conserved, the function and dynamics of actin in yeast, or more primitive systems, show some interesting differences. In this talk I will present results from a combination of simulations and mathematical modeling that provide new insight into the sequence-structure-function relationship in this important protein.