Abstract
Ste5 is a scaffold for the mitogen-activated protein kinase (MAPK) cascade components in a yeast pheromone response pathway. Ste5 also associates with Ste4, the beta subunit of a heterotrimeric guanine nucleotide-binding protein, potentially linking receptor activation to stimulation of the MAPK cascade. A RING-H2 motif at the Ste5 amino terminus is apparently essential for function because Ste5(C177S) and Ste5(C177A C180A) mutants did not rescue the mating defect of a ste5Delta cell. In vitro Ste5(C177A C180A) bound each component of the MAPK cascade, but not Ste4. Unlike wild-type Ste5, the mutant did not appear to oligomerize; however, when fused to a heterologous dimerization domain (glutathione S-transferase), the chimeric protein restored mating in an ste5Delta cell and an ste4Delta ste5Delta double mutant. Thus, the RING-H2 domain mediates Ste4-Ste5 interaction, which is a prerequisite for Ste5-Ste5 self-association and signaling.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing*
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Amino Acid Sequence
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Binding Sites
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism
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Carrier Proteins*
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Dimerization
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Fungal Proteins / chemistry*
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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GTP-Binding Protein beta Subunits*
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GTP-Binding Proteins / metabolism*
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Genetic Complementation Test
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Glutathione Transferase / chemistry
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Heterotrimeric GTP-Binding Proteins*
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Mating Factor
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Molecular Sequence Data
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Peptides / physiology*
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Pheromones / physiology
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Point Mutation
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Polymers
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae / chemistry
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins*
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Signal Transduction*
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Transformation, Genetic
Substances
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Adaptor Proteins, Signal Transducing
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Carrier Proteins
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Fungal Proteins
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GTP-Binding Protein beta Subunits
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Peptides
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Pheromones
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Polymers
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Recombinant Fusion Proteins
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STE5 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Ste4 protein, S cerevisiae
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Mating Factor
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Glutathione Transferase
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Calcium-Calmodulin-Dependent Protein Kinases
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GTP-Binding Proteins
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Heterotrimeric GTP-Binding Proteins