Protein phosphorylation, mediated by protein kinases, is a key event in the regulation of eukaryotic signal transduction. The majority of eukaryotic protein kinases perform phosphoryl transfer, assisted by two divalent metal ions. About 10% of all human protein kinases are, however, thought to be catalytically inactive. These kinases lack conserved residues of the kinase core and are classified as pseudokinases. Yet, it has been demonstrated that pseudokinases are critically involved in biological functions. Here, we show how pseudokinases have developed strategies by modifying amino acid residues in order to achieve stable, active-like conformations. This includes binding of the co-substrate ATP in a two metal-, one metal- or even no metal-binding mode. Examples of the respective pseudokinases are provided on a structural basis and compared with a canonical protein kinase, Protein Kinase A. Moreover, the functional roles of both independent metal-binding sites, Me1 and Me2, are discussed. Lack of phosphotransferase activity does not implicate a loss of function and can easily point to alternative roles of pseudokinases, i.e. acting as switches or scaffolds, and having evolved as components crucial for cellular cross-talk and signaling. Interestingly, pseudokinases are present in all kingdoms of life and their specific roles remain enigmatic. More studies are needed to unravel the crucial functions of those interesting proteins.
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Cover Image
Cover Image
An artistic model of the ‘molecular scissor’ ADAM10 (displayed in orange) at the cell surface, shown cleaving one of its substrates (green). ADAM10 is regulated by one of six TspanC8 tetraspanins (displayed in white or blue). The TspanC8s have distinct mechanisms of binding to ADAM10 and appear to dictate its substrate specificity. For more information, please see pages 719–730 in this issue of the Biochemical Society Transactions. Designer: Justyna Szyroka Artist: Eduardo Oliveira - Graphics Designer and Animator. Image kindly provided by Michael G Tomlinson.
Metal coordination in kinases and pseudokinases
Matthias J. Knape, Friedrich W. Herberg; Metal coordination in kinases and pseudokinases. Biochem Soc Trans 15 June 2017; 45 (3): 653–663. doi: https://doi.org/10.1042/BST20160327
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