The whole proteome dataset for the following eukaryotic species was included in the analysis: Homo sapiens, Mus musculus, Gallus gallus, Xenopus tropicalis, Danio rerio, Petromyzon marinus, Drosophila melanogaster, Caenorhabditis elegans, Saccharomyces cerviciae, Schistosoma mansoni, Apis mellifera, Anopheles gambiae, Pediculus humanus, Ixodes scapularis, Daphnia pulex, Oryza sativa, Pristionchus pacificus, Acyrthosiphon pisum, Trypanosoma brucei, Leishmania braziliensis and Ciona instestinalis were downloaded from Ensembl; Strongylocentrous purpuratus was downloaded from Spbase (www.spabase.org); Branchiostoma floridae, Nematostella vectensis, Trichoplax adhaerens, Phytophtera soyae, Thalassiosira pseudonana, Naegleria gruberi and Monosiga brevicollis were downloaded from the Joint Genome Institute; Dictyostelium discoideum was downloaded from dictyBase (www.dictybase.org); Arabidopsis thaliana was downloaded from TAIR (http://www.arabidopsis.org/); Entamoeba histolytica was downloaded from amoebaDB (http://amoebadb.org); Paramecium tetraurelia was downloaded from NCBI; Tetrahymena thermophila was downloaded from UniProt; Trichomonas vaginalis was downloaded from TrichDB (http://trichdb.org); Giardia lamblia was downloaded fromGiardiaDB (http://giardiadb.org).