ACTIN-LIKE ACTIN

The most biologically significant property of actin is its; ability to self-associate and form two-stranded polymeric microfilaments. In liv ing cells, these microfilaments form the actin cytoskeleton, essential for maintenance of the shape, passive mechanical properties and activ e motility of eukaryotic cells. Recently discovered actin-related prot eins (ARPs) appear to share a common ancestor with conventional actin. At present, six classes of ARPs have been discovered three of which h ave representatives in diverse species across eukaryotic phyla and may share functional characteristics with conventional actin. The three m ost ubiquitous ARPs are predicted to share a common core structure wit h actin and contain all the residues required for ATP binding. Surface residues involved in protein-protein interactions, however, have dive rged. Models of these proteins based on the atomic structure of actin provide some clues about how ARPs interact with each other, with conve ntional actin and with conventional actin-binding proteins.