Appeal No. 1995-4717
Application 07/876,288
protein in either the cytoplasm or the periplasm of E. coli. Cronan is also relied upon as
teaching that the fusion protein with a cleavage site would have allowed one to purify a
protein of interest, for example using affinity chromatography targeted towards the fusion
protein partner, and to subsequently cleave the purified protein from the fusion protein
partner at the cleavage site. Scott is cited (Answer, pages 7-8) as disclosing the use of
binding protein for screening random peptide libraries. Maina is cited as disclosing
(Answer, page 8) the use of E. coli vectors to express and purify foreign fusion proteins
and specifically exemplifies maltose binding protein as useful for this purpose. Finally,
Plückthun is relied upon for the disclosure that (Answer, page 7) "general solutions of
finding optimal ligands . . . will . . . be carried out outside the cell." The examiner then
concludes (Answer, pages 8-9):
As illustrated by the cited prior art, it was generally recognized that
generating libraries of a random or semi-random nature would have been
useful for a variety of purposes; for example, in elaborating the structure of
ligands of receptors or antibodies. Since the art recognized the concept of
using expression of random peptides in heterologous systems such a
bacteria, it would have been obvious to one of ordinary skill in the art at the
time the invention was made to use the expression vectors of Cronan et al.
to express random recombinant peptides because these vectors were
taught to be advantageous for purification and analysis of recombinantly
produced proteins. Many methods were available for generating
recombinant, random peptide libraries and the particular choice of vectors
as claimed was known at the time of the claimed invention.
It is the initial burden of the patent examiner to establish that claims presented in an
application for patent are unpatentable. In re Oetiker, 977 F.2d 1443, 1446, 24 USPQ2d
1443, 1445 (Fed. Cir. 1992). On the record before us, we find that the examiner has failed
to establish a prima facie case of unpatentability of the claimed subject matter.
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