Figure 1

The phylogenetic relationship of calpains from diverse evolutionary groups of eukaryotes. Only the catalytic core domains (dI-II) were used to construct the tree. Multiple alignments were done with Clustal X and bootstrapped with PAUP4* (1,000 iterations). Only values greater than 50% are indicated. The tree was rooted with the calpain-related sequence from the prokaryote Porphyromonas gingivalis. A minus sign (-) indicates a nonstandard catalytic triad; species names in bold contain EF-hand motifs and the amino- or carboxy-terminal location of the motif is indicated by superscript N or C. Gray box, representative examples of classical calpains; yellow box, calpains containing a carboxy-terminal SOL domain; magenta box, calpains containing an additional carboxy-terminal C2 domain (also referred to as a Tra3 or T domain); green box, calpains containing 21 amino-terminal transmembrane domains; blue box, calpains containing a carboxy-terminal PalB-type domain. Species names: T. brucei, Trypanosoma brucei; T. thermophila, Tetrahymena thermophila; S. histriomuscorum, Sterkiella histriomuscorum (a ciliate); E. histolytica, Entamoeba histolytica; D. melanogaster, Drosophila melanogaster; S. mansoni, Schistosoma mansoni; C. elegans, Caenorhabditis elegans; H. sapiens, Homo sapiens; A. thaliana, Arabidopsis thaliana; A. gambiae, Anopheles gambiae; C. albicans, Candida albicans; S. cerevisiae, Saccharomyces cerevisiae; P. falciparum, Plasmodium falciparum; C. parvum, Cryptosporidium parvum; P. gingivalis, Porphyromonas gingivalis. Calpains listed with unpublished, nonstandard abbreviations: 3TM, three carboxy-terminal transmembrane domains; 5EF, five-EF-hand motifs; 21TM, 21 amino-terminal transmembrane domains; DI-II, domains dI-dII-only calpain without further recognizable motifs. Single calpains have been identified in organisms where only species names are given. Sequences and accession numbers are available in Additional data file 1.