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Molecular and Cellular Biology, April 2008, p. 2481-2494, Vol. 28, No. 7
0270-7306/08/$08.00+0     doi:10.1128/MCB.01817-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Two Adjacent Docking Sites in the Yeast Hog1 Mitogen-Activated Protein (MAP) Kinase Differentially Interact with the Pbs2 MAP Kinase Kinase and the Ptp2 Protein Tyrosine Phosphatase ^,

Yulia Murakami, Kazuo Tatebayashi, and Haruo Saito^*

Division of Molecular Cell Signaling, Institute of Medical Sciences, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan, and Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

Received 5 October 2007/ Returned for modification 9 November 2007/ Accepted 14 January 2008

Functional interactions between a mitogen-activated protein kinase (MAPK) and its regulators require specific docking interactions. Here, we investigated the mechanism by which the yeast osmoregulatory Hog1 MAPK specifically interacts with its activator, the MAPK kinase Pbs2, and its major inactivator, the protein phosphatase Ptp2. We found, in the N-terminal noncatalytic region of Pbs2, a specific Hog1-binding domain, termed HBD-1. We also defined two adjacent Pbs2-binding sites in Hog1, namely, the common docking (CD) domain and Pbs2-binding domain 2 (PBD-2). The PBD-2 docking site appears to be sterically blocked in the intact Hog1 molecule, but its affinity to Pbs2 is apparent in shorter fragments of Hog1. Both the CD and the PBD-2 docking sites are required for the optimal activation of Hog1 by Pbs2, and in the absence of both sites, Hog1 cannot be activated by Pbs2. These data suggest that the initial interaction of Pbs2 with the CD site might induce a conformational change in Hog1 so that the PBD-2 site becomes accessible. The CD and PBD-2 docking sites are also involved in the specific interaction between Hog1 and Ptp2 and govern the dynamic dephosphorylation of activated Hog1. Thus, the CD and the PBD-2 docking sites play critical roles in both the activation and inactivation of Hog1.

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* Corresponding author. Mailing address: Institute of Medical Sciences, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan. Phone: 1-81-3-5449-5505. Fax: 1-81-3-5449-5701. E-mail: h-saito{at}ims.u-tokyo.ac.jp

Published ahead of print on 22 January 2008.

Supplemental material for this article may be found at http://mcb.asm.org/.

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Molecular and Cellular Biology, April 2008, p. 2481-2494, Vol. 28, No. 7
0270-7306/08/$08.00+0     doi:10.1128/MCB.01817-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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