Sequence alignments of asteropsins A–D (ASPA, ASPB, ASPC, and ASPD). The disulfide bonds are connected by solid lines. Residues: red = acidic, blue = basic, yellow = Cys, purple = Pro. X = pyroglutamic acid. The seven conserved residues involved in structural maintenance are marked with boxes, and the loops indicate the residues comprising polypeptide backbones between two Cys residues. Sequence alignment was performed with ClustalX 2.0.