Saposin protein N-terminal–C-terminal helical disulfide strain of members of the Saposin family deposited in the Protein Data Bank determined with X-ray crystallography and high-resolution NMR spectroscopy.

Distance and disulfide strain energy were calculated using the disulfide bond dihedral angle energy server available through the IGP Institute for Genomics and Proteomics US Department of Energy Office of Science at UCLA (https://services.mbi.ucla.edu), based on the formalism of Katz et al. [62]. This web based utility uses the following equation: E(kJ/mol = 8.37(1+cos(3x1)) + 8.37(1+cos(3x1’)) = 4.18(1 + cos(3x2)) + 4.18(1+cos(3x2’)) + 14.64(1 +cos(2x3)) + 2.51(1+cos(3x3)) described in the original paper to provide the above energetic estimates. The server measures the dihedral angles and calculates a dihedral energy for all disulfide bonds found in the uploaded PDB coordinate file. Values for disulfide distance and strain energy are the mean and standard deviation (±) for the ten lowest energy conformers of the PDB coordinate set. No statistical estimates are available for PDB accession codes 4DDJ.PDB, 2GTG.PDB, and 5U85.PDB since the deposition has only one coordinate set for the protein.