Interference 102,728
(Kurjan, U.S. Patent No. 4,546,082), col. 3, lines 7-10. The " factor protein controls
mating between yeast cells which have the opposite mating type. Id, lines 32-35.
Important, for purposes of this interference, however, are the elements of the "-factor
protein which enable it to be secreted.
Alpha factor is synthesized as a large, precursor molecule which contains
several tandem copies of the " factor protein. Id., col. 4, lines 8-10. The copies of the
" factor protein are separated from one another by a spacer region of six (6) amino
acids which (from the N-terminus to C-terminus) are: lys-arg-glu-ala-glu-ala- .5 Id.,
lines 17-18. The amino acids of the spacer sequence are substrates for two yeast
enzymes, KEX2 (which cleaves the spacer sequence after the arg residue), and
dipeptidylaminopeptidase A (DPAP A- which cleaves after each ala residue). Brake
Brief, Paper No. 190, pp. 9-10. This cleavage by the yeast enzymes results in the
release of mature " factor protein.6 Id. In addition, the precursor molecule contains a
“leader sequence which allows for transport of the " factor proteins through the outer
cell membrane [of the yeast cell] and into the surrounding environment.” Id., p. 8.
Thus, simply stated, the structure of the precursor molecule in yeast is as follows:
Leader- [lys-arg-glu-ala-glu-ala]-" factor- [lys-arg-glu-ala-glu-ala]-" factor ...
5 A.k.a., lysine-arginine-glutamine-alanine-glutamine-alanine-.
6 A “mature” protein is one which lacks any extraneous amino acids. Thus, the
cleavage of the spacer sequence with KEX2 and DPAP A results in the production of
“pure” " factor. We note that there is a third enzyme which cleaves following the final
amino acid of the " factor protein which is necessary to release mature " factor. Brake
Brief, Paper No. 190, pp. 9-10. However, as pointed out by Brake, this enzyme is not
relevant to the invention of this interference. Id.
4
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