Yeast MEK-dependent signal transduction: response thresholds and parameters affecting fidelity.
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.
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599, USA.
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B
Yashar
K
K
Irie
J A
JA
Printen
B J
BJ
Stevenson
G F
GF
Sprague
K
K
Matsumoto
B
B
Errede
D000483:Alleles; D000595:Amino Acid Sequence; D003433:Crosses, Genetic; D005800:Genes, Fungal; D014644:Genetic Variation; D005838:Genotype; D006639:Histidine / Q000378:metabolism; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011494:Protein Kinases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction
D011994:Recombinant Proteins; D006639:Histidine; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases