Phylogenetic comparisons of actin and actin-related proteins in apicomplexans and model organisms. In addition to conventional actins, apicomplexans contain conserved Arp1, Arp4, and Arp6 proteins; however, they do not encode Arp2 or Arp3 orthologues. Many apicomplexan proteins do not group with any of the known Arp clades. These have been divided further into proteins that are highly conserved among all the apicomplexans (i.e. ALP1, ALP2, ALP3) and those that are organism-specific (i.e. ALP5, ALP7, ALP8). Phylogenetic analysis was performed using PAUP*4.0b10 and the BioNeighbor-Joining algorithm (BioNJ) to determine the divergence distances among taxa. Consensus trees were bootstrapped for 1000 replicates and drawn according to the 50% majority-rule. Conventional actin was defined as the out-group. Subgroups of Arps and ALPs have been highlighted to define the boundaries between groups. Taxa are as follows: At = Arabidopsis thaliana, Bs = Bacillus subtilis, Ce = Caenorhabditis elegans, Cp = Cryptosporidium parvum, Dd = Dictyostelium discodium, Dm = Drosophila melanogaster, Hs = Homo sapiens, Pf = Plasmodium falciparum, Sc = Saccharomyces cerevisiae, Tg = Toxoplasma gondii, Tp = Theileria parva, Tt = Tetrahymena thermophila. Bootstrap values ≥90% are represented by the black nodes ●, values ≥ 75% are represented by the gray nodes , and values ≥50% are denoted by the white nodes ○.