Appeal No. 1999-1355 Page 9
Application No. 08/469,786
Hopp explicitly states that “[t]he identification peptide is . . . a linear sequence of
amino acids bonded to the N-terminus of the protein of interest” (emphasis added) and
“is composed of two basic portions: an antigenic N-terminus or ‘head’ portion; and a
linking or ‘tail’ portion to link the identification peptide to the selected protein molecule.”
Column 5, lines 9-15. The linking portion of the identification peptide is “composed of a
sequence of amino acids ending with either Lys, Arg, Met or Asn, so that “a proteolytic
enzyme that cleaves after the Arg or Lys residue can be used . . . or an appropriate
chemical agent that cleaves after [Met or Asn] may be employed to sever the
identification peptide from the protein molecule” (Column 6, lines 4-12), “ideally at the
residue adjacent the N-terminus of the protein molecule” (Column 5, lines 51-55).
“By this particular construction of the identification peptide, the hybrid . . . molecules
expressed by the transformed host cells can be isolated by affinity chromatography
techniques . . . [and] the identification peptide [can be] cleaved from the protein
molecule . . . releasing the desired, highly purified protein.” Column 2, line 63 to
column 3, line 7. Clearly, the orientation of the two moieties of the protein-peptide
hybrid is dictated by Hopp’s ultimate goal: isolation and purification of the selected
protein.
In responding to appellants’ comments on this issue, the examiner argues
(Answer, page 24) that
One of ordinary skill in the art would have known that the genetic material
encoding the immunoglobulin constant region is 3' to the genetic material
encoding the variable region of an antibody chain . . . [and] would have
constructed the gene of the Ig-protein chimera analogous to the structure
of the Ig gene constructs containing the variable and constant region gene
segments . . . since anyone of ordinary skill in the art would also have
known that a functional antibody has a variable region domain in the
protein that is antigen specific and [Hopp] as well as each of [Neuberger]
or [Cabilly] teach maintenance of that variable region antigen binding
domain.
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