Appeal No. 1995-4867
Application 07/993,482
Thus, one seeking to secrete foreign proteins from an E. coli host cell using knowledge
from Chang would only reasonably expect the protein to be found in the periplasm, not in
the culture medium due to the outer cell membrane wall. Miyake states in the paragraph
bridging the columns on page 1429 that the secretion mechanism in E. coli is still
unknown. Miyake sets forth in the first full paragraph of the left hand column of page 1430
their expectation that a chimeric protein “should be transported across the inner
membrane to the periplasmic space as a mature form” where it can be extracted and
recovered. All of these disclosures teach away from an expectation of successfully
constructing an expression cassette having the properties required by claim 31 on appeal.
In our view, these teachings provide evidence that constructing an expression
cassette capable of the ”secretion of a disulfide bond-containing polypeptide in a
biologically active, mature form from an E. coli host cell into the culture medium” would
have been highly problematic at the time of the present invention. To whatever extent it
may be concluded that it would have been obvious to select the components of the DNA
segment of claim 31 and arrange them in the manner required by that claim, we do not find
that the prior art relied upon would have reasonably suggested that such an expression
cassette would allow for the secretion of a disulfide bond-containing polypeptide in a
biologically active, mature form from an E. coli host cell into the culture medium.”
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