Selenoproteomes and the Sec content of SelPs. Taxonomic tree, Sec and Cys content of SelPs (left panel) and selenoproteomes of vertebrates with completely or partially sequenced genomes (right panel) are shown. Red circles with ticks show the presence of selenoproteins. Blue circles with ticks indicate the presence of Cys-containing homologs. Crossed black circles are used to show the loss of protein during evolution. Similarly, red and blue squares are used to indicate Sec and Cys residues in SelP sequences, respectively. Dotted lines (empty cells) correspond to undetected sequences in genomes with low sequence coverage.