Appeal No. 2001-1436 Page 10
Application No. 08/422,612
functionally expressed in S. cerevisiae because S. cerevisiae was
already known to naturally produce G proteins and G protein-
coupled receptors and the functional expression of other
mammalian receptor proteins in S. cerevisiae was a routine
practice in the art at the time of the instant invention.
Appellants, however, point out the lack of support for the examiner’s
position that “this partial complement would require the rat Gα subunit to
functionally interact (couple) with the endogenous mating factor receptor of the
host cell.” Specifically, Appellants point to Dietzel’s discussion of their
experimental data. See the Appeal Brief, pages 52-57. Dietzel concludes that
their data can be explained by either of two models, shown in Figure 6. In both
of the models, the rat G protein α subunit does not interact with the yeast
receptor protein. See page 1007, right-hand column (emphasis added):
Both models are consistent with the phenotypes associated with
SCG1 and with the ability of rat αs [α subunit] to complement an
scg1 mutation.
. . . The mating defect of the scg1 mutants expressing rat αs
suggests that this heterologous protein is not able to interact with
activated a- or α-factor receptor; therefore, GDP-GTP exchange
would not occur in either model, resulting in an inability to activate
the pheromone response pathway.
We agree with Appellants that Dietzel’s conclusion would have led those
of skill in the art to doubt the success of combining a mammalian G protein-
coupled receptor gene with Dull’s yeast assay system. Specifically, Dietzel’s
conclusion that a mammalian G protein α subunit did not interact with the yeast
receptor would lead those skilled in the art to reasonably expect that the yeast G
protein α subunit would also not interact with a mammalian receptor. Therefore,
those skilled in the art would expect that a mammalian G protein-coupled
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