Activation and inhibition of the C-terminal kinase domain of p90 ribosomal S6 kinases

This is the authors' abstract. We don't add key points for this paper.

The p90 ribosomal S6 kinases (RSKs) contain two distinct catalytic kinase domains, the N-terminal and C-terminal kinase domains (NTKD and CTKD, respectively). The activation of CTKD is regulated by phosphorylation by extracellular signal–regulated kinase (ERK1/2) and an autoinhibitory αL helix. Through a mutational series in vitro of the RSK CTKDs, we found a complex mechanism lifting autoinhibition that led us to design constitutively active RSK CTKDs. These are based on a phosphomimetic mutation and a C-terminal truncation (e.g., RSK2 T577E D694*) where a high activity in absence of ERK phosphorylation is obtained. Using these constructs, we characterize IC 50 values of ATP-competitive inhibitors and provide a setup for determining specificity constants (k inact /K i ) of covalent CTKD inhibitors.