Product and process for introduction of a hinge region into a fusion protein to facilitate cleavage

A method of producing a selected target polypeptide expressed by a host cell culture, said method comprising the steps of:

• a. expressing a fused polypeptide by culturing said host cell culture, the cells of said culture containing and being capable of expressing a recombinant DNA encoding said fused polypeptide, said fused polypeptide comprising:
• a first sequence of amino acids defining a leader sequence, a hinge region, and at least one amino acid defining a cleavage site recognizable and cleavable by a selected cleavage agent,
• said hinge region being a cysteine-free flexible amino acid sequence not normally associated with said leader sequence or said target polypeptide and comprising at least two amino acids defining a secondary structure which can promote cleavage by said cleavage agent at said cleavage site;
• and
• a second sequence of amino acids linked to said first sequence defining a said selected target polypeptide;
• b. exposing said fused polypeptide to said selected cleavage agent in an environment wherein said target polypeptide is disposed in its three dimensional conformation and said selected cleavage agent is rendered preferentially accessible to said cleavage site by said hinge region thereby to cleave said target polypeptide from the remainder of said fused polypeptide preferentially at said cleavage site;
• and
• c. separating said target polypeptide from the remainder of said fused polypeptide.