Phosphorylation of a conserved intrinsically disordered region is necessary for activation of a bacterial Hanks-type Ser/Thr kinase signaling pathway

Intrinsically disordered regions (IDRs) are found throughout all domains of life, yet their contribution to bacterial signaling has remained unclear. Here we show that phosphorylation of a conserved juxtamembrane IDR is necessary for activation of the bacterial Hanks-type Ser/Thr kinase-phosphatase PrkC/PrpC signaling pathway in Bacillus subtilis. Phosphoablative mutation of a conserved IDR phosphosite has strong effect on kinase-activity-dependent phenotypes, including intrinsic β-lactam resistance and stationary phase survival. Using a synthetic quantitative reporter for kinase activity, mutational analysis, and mathematical modeling, we show that phosphorylation of the IDR promotes trans autoactivation of the kinase, and that this modification is essential for amplifying kinase activity in response to a signal. Phylogenetic analysis demonstrates that this IDR and associated putative phosphosites proximal to the kinase domain are highly conserved across prokaryotic species that diverged at the last universal common ancestor. Together these findings suggest that kinase-domain proximal IDR phosphorylation has a critical role in bacterial Ser/Thr signaling, with direct implications for understanding antibiotic resistance mechanisms and developing kinase-targeting antimicrobials.