 Actin isoforms are structurally conserved but have subtle differences in their design which affects their interactions with other proteins. These differences can be seen in the structures of skeletal muscle alpha actin, cardiac muscle alpha actin, beta actin, and gamma actin. The structures provide insight into the mechanisms by which these isoforms interact with each other and with myosin motors and actin binding proteins. This knowledge will help us better understand the normal function of eukaryotic cells. This article was authored by Amandeep Esorora, Chiong Ling Huang, Roman Pritzing, and others.