Affiliation:
1. Departments of Biochemistry
2. Biological Sciences
3. Genetics Program, University of Iowa, Iowa City, Iowa 52242
Abstract
ABSTRACT
The
SLN1
two-component signaling pathway of
Saccharomyces cerevisiae
utilizes a multistep phosphorelay mechanism to control osmotic stress responses via the
HOG1
mitogen-activated protein kinase pathway and the transcription factor Skn7p. Sln1p consists of a sensor kinase module that undergoes histidine autophosphorylation and a receiver module that autocatalytically transfers the phosphoryl group from histidine to aspartate. The Sln1p aspartyl phosphate is then transferred to Ypd1p, which in turn transfers the phosphoryl group to a conserved aspartate on one of two response regulators, Ssk1p and Skn7p. Activated alleles of
SLN1
(
sln1*
) were previously identified that appear to increase the level of phosphorylation of downstream targets Ssk1p and Skn7p. In principle, the phenotype of
sln1
* alleles could arise from an increase in autophosphorylation or phosphotransfer activities or a decrease in an intrinsic or extrinsic dephosphorylation activity. Genetic analysis of the activated mutants has been unable to distinguish between these possibilities. In this report, we address this issue by analyzing phosphorelay and phosphohydrolysis reactions involving the Sln1p-associated receiver. The results are consistent with a model in which the activated phenotype of the
sln1
* allele,
sln1
-
22
, arises from a shift in the phosphotransfer equilibrium from Sln1p to Ypd1p, rather than from impaired dephosphorylation of the system in response to osmotic stress.
Publisher
American Society for Microbiology
Subject
Molecular Biology,General Medicine,Microbiology
Cited by
7 articles.
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