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Published August 11, 2006 | public
Journal Article

A Dimeric Kinase Assembly Underlying Autophosphorylation in the p21 Activated Kinases


The p21-activated kinases (PAKs) are serine/threonine kinases that are involved in a wide variety of cellular functions including cytoskeletal motility, apoptosis, and cell cycle regulation. PAKs are inactivated by blockage of the active site of the kinase domain by an N-terminal regulatory domain. GTP-bound forms of Cdc42 and Rac bind to the regulatory domain and displace it, thereby allowing phosphorylation of the kinase domain and maximal activation. A key step in the activation process is the phosphorylation of the activation loop of one PAK kinase domain by another, but little is known about the underlying recognition events that make this phosphorylation specific. We show that the phosphorylated kinase domain of PAK2 dimerizes in solution and that this association is prevented by addition of a substrate peptide. We have identified a crystallographic dimer in a previously determined crystal structure of activated PAK1 in which two kinase domains are arranged face to face and interact through a surface on the large lobe of the kinase domain that is exposed upon release of the auto-inhibitory domain. The crystallographic dimer is suggestive of an engagement that mediates trans-autophosphorylation. Mutations at the predicted dimerization interface block dimerization and reduce the rate of autophosphorylation, supporting the role of this interface in PAK activation.

Additional Information

© 2006 Elsevier Ltd. Received 29 March 2006, Revised 8 June 2006, Accepted 9 June 2006, Available online 27 June 2006. We thank David King and Arnold Falick for mass spectrometry analysis of phosphorylated proteins and peptide synthesis. We also thank Stephen Harrison for sharing the coordinates to the PAK1 kinase domain structures prior to publication. Lastly, we thank Erica Chou for assistance during the initial stages of the project, and all the members of our laboratories for assistance and support. M. P. is supported by the Molecular Biophysics NIH-GM-08295 training grant. We thank NSF and NIH NMR instrumentation grants (NSF 0119304 and NIH RR15756).

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