Oh yes, I'd forgotten about the less common MEX and ABU cases. Yes,
those are also mapped, to CYS.
Because when MODELLER is integrated with other programs, some do not
make the same choice of automatically treating HETATM MSE as ATOM MET
and this can lead to confusion. I think this behaviour should not be
hardcoded.
Makes sense. I'll add an option to turn this off in the next release.
Additionnally, I think your mapping of MSE SE atom to MET SD atom is slightly
incorrect in the eyes of the PDB standard: