Abstract
Actin is the best-studied member of a family of ATPases that originated, presumably via gene duplications, in the common ancestor of all living things.The discovery of actin-related proteins (ARPs) and the resolution of the three-dimensional structure of actin has refueled interest in the phylogeny of this coding region.In comparison to vertebrates and land plants, relatively little is known, however, about actin and actin gene families in protists.In this paper, the origin of actin is reviewed and sequence analyses of this coding region are presented.Phylogenetic analyses of actins are used to probe the evolutionary relationships between actin isoforms in three lineages, the prymnesiophytes (Le.
Emiliana huxleyi), the heterokonts and the green~,algae/land plants, and the relationships between these sequences with actins from diverse eukaryotes.