Genetics, Vol. 163, 507-514, February 2003, Copyright © 2003

Std1p (Msn3p) Positively Regulates the Snf1 Kinase in Saccharomyces cerevisiae

Sergei Kuchina, Valmik K. Vyasb, Ellen Kantera, Seung-Pyo Honga, and Marian Carlsona,b
a Departments of Genetics and Development and Microbiology, Molecular and Biophysical Studies, Columbia University, New York, New York 10032
b Integrated Program in Cellular, Molecular and Biophysical Studies, Columbia University, New York, New York 10032

Corresponding author: Marian Carlson, HSC922, New York, NY 10032., mbc1{at}columbia.edu (E-mail)

Communicating editor: B. J. ANDREWS

The Snf1 protein kinase of the glucose signaling pathway in Saccharomyces cerevisiae is regulated by an autoinhibitory interaction between the regulatory and catalytic domains of Snf1p. Transitions between the autoinhibited and active states are controlled by an upstream kinase and the Reg1p-Glc7p protein phosphatase 1. Previous studies suggested that Snf1 kinase activity is also modulated by Std1p (Msn3p), which interacts physically with Snf1p and also interacts with glucose sensors. Here we address the relationship between Std1p and the Snf1 kinase. Two-hybrid assays showed that Std1p interacts with the catalytic domain of Snf1p, and analysis of mutant kinases suggested that this interaction is incompatible with the autoinhibitory interaction of the regulatory and catalytic domains. Overexpression of Std1p increased the two-hybrid interaction of Snf1p with its activating subunit Snf4p, which is diagnostic of an open, uninhibited conformation of the kinase complex. Overexpression of Std1p elevated Snf1 kinase activity in both in vitro and in vivo assays. These findings suggest that Std1p stimulates the Snf1 kinase by an interaction with the catalytic domain that antagonizes autoinhibition and promotes an active conformation of the kinase.




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