Figure 1

Taxonomic distribution of calpain variants (left side) revealed by comparison of genomes from 44 eukaryotic species (top section). Black circles indicate calpains with all three active site residues (Cys, His, Asn) intact in the CysPc domain. Grey circles indicate that the three CysPc active site residues are partially or completely substituted or missing. Half black and half grey circles indicate that some of detected calpains had all three residues, whereas others lacked at least one of the active residues. Black dots show that the calpain domain combination is absent. * indicates a novel domain combination identified in this work. All calpains are listed with accession numbers in Additional file 1: Table S1.