Appeal No. 1996-0223
Application No. 07/931,563
Vitamin-K dependent proteins, i.e., Factor IX, Factor X, Factor VII, prothrombin, protein S
and protein C, all contain metal binding amino acid (-carboxyglutamic acid. When these proteins
complex with metal ions, e.g., calcium, magnesium, manganese and gadolinium ions, they undergo a
structural conformational change that includes changes in the three-dimensional structure of the (-
carboxyglutamic acid-rich regions of the proteins. (specification, pages 2, 5-6)
THE INVENTION
As succinctly stated by appellants, the claimed invention is directed to
... methods for purifying vitamin-K dependent proteins with conformation-specific
antibodies that react only with (i) specific protein-cation complexes (claims 2, 3, 5, 6-8,
17, 23-28, and 32) or (ii) specific cation-free uncomplexed proteins (claims 10, 11,
and 13-15). In these methods, the protein to be purified forms an immune complex
with a conformation-specific antibody, and is then released from the immune complex
by induction of a conformational change of the protein so that it is no longer recognized
by the antibody.
When the antibody is specific for the protein-cation complex, the protein is
removed from the immune complex by exposing the complex to a compound, e.g., a
chelating-agent, that has a higher binding affinity for the cation than does the protein.
This compound removes the cation from the protein to induce a non-stabilized
conformational state that is not recognized by the antibody, which disrupts the protein-
antibody complex.
When the antibody binds exclusively to a cation-free protein, the protein is
removed from the immune complex by exposing the complex to a metal cation that
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