Structural insights into autophosphorylation-mediated heat shock response by the protein-arginine kinase McsAB

McsAB is a protein-arginine kinase that activates heat shock genes by inhibiting the transcriptional repressor CtsR. However, the mechanism by which McsAB suppresses CtsR during heat shock remains unclear. Here, we present cryo-electron microscopy structures of Bacillus subtilis McsAZ2-McsB and its complex with CtsR. Our structural analyses reveal that McsAZ2-McsB forms a rod-shaped heterotetramer, with two of these heterotetramers assembling into an asymmetrically crossing shape through phosphorylated arginine residues (pArg194 and pArg333) of McsB. The CtsR dimer binds to the groove of the McsAZ2-McsB oligomer via pArg115 of McsA and pArg194 of McsB. Anisotropy experiments indicate that CtsR dissociates slowly from its operator during heat shock, and McsAB facilitates this process in an ATP-dependent manner. Furthermore, mutations in the arginine residues of McsAB reduce its ability to hijack CtsR during heat shock. These results demonstrate that autophosphorylation of McsAB is essential for a rapid and effective heat shock response.