Ribbon representations of the 3D structures of 2FS1 (a) and 1PGA(b) with their amino acid sequences. A segment with dark gray denotes an α helix and one with light gray denotes a β strand. A residue with the symbol "a" takes the α-helix conformation and one with "b" takes a β-strand conformation. The definition of the secondary structures in the PDB is used in this study. All identical residues between the two sequences are highlighted.