Appeal No. 2001-1436 Page 9
Application No. 08/422,612
subunit converts the bound GTP back to GDP, and reassociates with the β and γ
subunits, resetting the system to its resting state.
Thus, the extracellular signal (the receptor binding its ligand) is transduced
into an intracellular signal (effector protein activity) through the interaction of the
receptor with the G protein α subunit. The skilled artisan would therefore expect
that if the receptor could not interact with the G protein α subunit, the G protein
would not dissociate, and no signal would be produced, in response to the
ligand/receptor binding. The disclosure of the Dietzel reference must be
considered in light of this expectation.
Dietzel isolated a yeast gene encoding a protein involved in the mating
factor (pheromone) response pathway. Dietzel concluded, based on sequence
homology and structural features, that the protein was a homolog of a G protein α
subunit and named the gene SCG1, for Saccharomyces cerevisiae G protein
gene. See page 1001. Dietzel also showed that yeast strains having mutations
in the SCG1 gene could be partially complemented by a mammalian (rat) gene
encoding a G protein α subunit. See pages 1005-1006.
The examiner relies on this complementation to provide an expectation of
success. See the Examiner’s Answer, pages 9-10:
Since this partial complement would require the rat Gα subunit to
functionally interact (couple) with the endogenous mating factor
receptor of the host cell as well as the S. cerevisiae Gβ and Gγ
subunits and/or downstream effectors as illustrated in Figure 6
therein, then this reference shows that the S. cerevisiae mating
factor receptors are, by definition, G protein-coupled receptors
since they transduce their ligand activated signals directly through
G proteins. . . . Th[e] artisan had more than a reasonable
expectation that a mammalian G protein-coupled receptor could be
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