Component of the polarisome%3B functions in actin cytoskeletal organization during polarized growth%3B acts as a scaffold for Mkk1p and Mpk1p cell wall integrity signaling components%3B potential Cdc28p substrate%3B coding sequence contains length polymorphisms in different strains%3B SPA2 has a paralog%2C SPH1%2C that arose from the whole genome duplication