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Mol. Cell. Biol., 12 1995, 6545-6553, Vol 15, No. 12
B Yashar, K Irie, JA Printen, BJ Stevenson, GF Sprague Jr, K Matsumoto and B Errede
Ste7p and Mkk1p are MEK (MAPK/ERK kinase) family members that function in
the mating and cell integrity signal transduction pathways in Saccharomyces
cerevisiae. We selected STE7 and MKK1 mutations that stimulated their
respective pathways in the absence of an inductive signal. Strikingly,
serine-to-proline substitutions at analogous positions in Ste7p (position
368) and Mkk1p (position 386) were recovered by independent genetic
screens. Such an outcome suggests that this substitution in other MEKs
would exhibit similar properties. The Ste7p-P368 variant has higher basal
enzymatic activity than Ste7p but still requires induction to reach full
activation. The higher activity associated with Ste7p-P368 allows it to
compensate for defects in the cell integrity pathway, but it does so only
when it is overproduced or when Ste5p is missing. This behavior suggests
that Ste5p, which has been proposed to be a tether for the kinases in the
mating pathway, contributes to Ste7p specificity.
Copyright © 1995, American Society for Microbiology
Yeast MEK-dependent signal transduction: response thresholds and parameters affecting fidelity
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599, USA.
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