The from_pdb command reads a PDB format coordinate file and writes, at least, a TNT coordinate file. If a sequence file did not exist one will be created. If there was no TNT control file one will be created which contains only limited information. You will have to edit this control file prior to executing any other TNT commands.
If the PDB file contains a proper CRYST1 card a TNT control file is
not required for this command. This is the only TNT shell command which
will run without a control file. If the PDB file does not contain the cell
constants on a CRYST1 card you must create a TNT control file which supplies
this information.