Conservation of the PCSK catalytic domain. The 3D-structure of mouse FURIN is shown as surface (left) and cartoon (right) presentation and the bound inhibitor as purple stick model. Amino acids identical in >95% of the 152 related PCSK sequences are marked with green color, indicating highly conserved active site. Sequences that were used for the analysis are available in the Additional File 1. Some of the conserved residues are labeled using the FURIN numbering.