Crystal structure of the Ca²?/calmodulin-dependent protein kinase kinase in complex with the inhibitor STO-609.

ABSTRACT: Ca(2+)/calmodulin (CaM)-dependent protein kinase (CaMK) kinase (CaMKK) is a member of the CaMK cascade that mediates the response to intracellular Ca(2+) elevation. CaMKK phosphorylates and activates CaMKI and CaMKIV, which directly activate transcription factors. In this study, we determined the 2.4 Å crystal structure of the catalytic kinase domain of the human CaMKK? isoform complexed with its selective inhibitor, STO-609. The structure revealed that CaMKK? lacks the ?D helix and that the equivalent region displays a hydrophobic molecular surface, which may reflect its unique substrate recognition and autoinhibition. Although CaMKK? lacks the activation loop phosphorylation site, the activation loop is folded in an active-state conformation, which is stabilized by a number of interactions between amino acid residues conserved among the CaMKK isoforms. An in vitro analysis of the kinase activity confirmed the intrinsic activity of the CaMKK? kinase domain. Structure and sequence analyses of the STO-609-binding site revealed amino acid replacements that may affect the inhibitor binding. Indeed, mutagenesis demonstrated that the CaMKK? residue Pro(274), which replaces the conserved acidic residue of other protein kinases, is an important determinant for the selective inhibition by STO-609. Therefore, the present structure provides a molecular basis for clarifying the known biochemical properties of CaMKK? and for designing novel inhibitors targeting CaMKK? and the related protein kinases.

SUBMITTER: Kukimoto-Niino M 

PROVIDER: S-EPMC3121401 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature