Representation of protein domains and identified sectors in the 3D structure of spermine synthase (PDB: 3C6K). A) Protein domains were colored in one of the chains of the homodimer. Red corresponds to the N-terminal domain, the long loop is in purple, the beta strand domain is in yellow, and the C-terminal region is in blue, with the catalytic center shown in light blue. B) Identified protein sectors in spermine synthase. Each sector is represented with a different color, and appears to have a distribution that is not limited to the described domains.