Data items in the PDBX_CONSTRUCT category specify a sequence of
nucleic acids or amino acids. It is a catch-all that may be used to
provide details of sequences known to be relevant to the project as well
as primers, plasmids, proteins and such like that are either used or
produced during the protein production process. Molecules described
here are not necessarily complete, so for instance it would be
possible to include either a complete plasmid or just its insert.
This category may be considered as an abbreviated form of _entity where
the molecules described are not required to appear in the final co-ordinates.
Note that the details provided here all pertain to a single entry as defined
at deposition. It is anticipated that _pdbx_construct.id would also be
composed of a sequence that is unique within a given site prefixed by a code
that identifies that site and would, therefore, be GLOBALLY unique. Thus
this category could also be used locally to store details about the different
constructs used during protein production without reference to the entry_id
(which only becomes a meaningful concept during deposition).