title: Structural insights into the activation of MST3 by MO25.
abstract: The MO25 scaffolding protein operates as critical regulator of a number of STE20 family protein kinases (e.g. MST and SPAK isoforms) as well as pseudokinases (e.g. STRAD isoforms that play a critical role in activating the LKB1 tumour suppressor). To better understand how MO25 interacts and stimulates the activity of STE20 protein kinases, we determined the crystal structure of MST3 catalytic domain (residues 19-289) in complex with full length MO25β. The structure reveals an intricate web of interactions between MST3 and MO25β that function to stabilise the kinase domain in a closed, active, conformation even in the absence of ATP or an ATP-mimetic inhibitor. The binding mode of MO25β is reminiscent of the mechanism by which MO25α interacts with the pseudokinase STRADα. In particular we identified interface residues Tyr223 of MO25β and Glu58 and Ile71 of MST3 that when mutated prevent activation of MST3 by MO25β. These data provide molecular understanding of the mechanism by which MO25 isoforms regulates the activity of STE20 family protein kinases.
authors.affiliation: MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH Scotland, UK. y.mehellou@dundee.ac.uk
authors.forename: Youcef
authors.initials: Y
authors.lastname: Mehellou
authors.forename: Dario R
authors.initials: DR
authors.lastname: Alessi
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Macartney
authors.forename: Marta
authors.initials: M
authors.lastname: Szklarz
authors.forename: Stefan
authors.initials: S
authors.lastname: Knapp
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Elkins
mesh_terms: D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry*; D017433:Protein Structure, Secondary; D000099317:Hippo Kinases
chemical_list: D002135:Calcium-Binding Proteins; D009419:Nerve Tissue Proteins; D017346:Protein Serine-Threonine Kinases; C540569:CAB39 protein, human; C118135:OXSR1 protein, human; C109163:STK24 protein, human; D000099317:Hippo Kinases; C486409:STK39 protein, human