Disclosed is a process for preparing a pharmacologically active compound, in which at least one internal conjugation site of an Fc domain sequence is selected that is amenable to conjugation of an additional functional moiety by a defined conjugation chemistry through the side chain of an amino acid residue at the conjugation site. An appropriate amino acid residue for conjugation may be present in a native Fc domain at the conjugation site or may be added by insertion (i.e., between amino acids in the native Fc domain) or by replacement (i.e., removing amino acids and substituting different amino acids). In the latter case, the number of amino acids added need not correspond to the number of amino acids removed from the previously existing Fc domain. This technology may be used to produce useful compositions of matter and pharmaceutical compositions containing them.； A DNA encoding the inventive composition of matter, an expression vector containing the DNA, and a host cell containing the expression vector are also disclosed.
