Activation mechanism of the full-length histidine kinase LvrB from pathogenic Leptospira.

Pathogenic Leptospira modulate their virulence via the Lvr signaling system, with the histidine kinase LvrB being a central element. LvrB is a prototype of Rec-controlled histidine kinases, which are frequently found in bacterial two-component systems, and yet whose regulatory mechanisms remain largely unknown. Here, we report full-length structures of LvrB in different states uncovering its mechanism of activation. Kinase-inactive LvrB is a symmetric homodimer, with its catalytic domains rigidly clasped onto the central helical domain. Phosphorylation of the N-terminal Rec domains induces coiled-coil formation of the central αS helices thereby breaking symmetry through liberation of the catalytic domains into a dynamic, auto-phosphorylation competent state. We further identified LvrB's downstream effector partner LvrC, an anti-σ factor that reprograms the transcription of hundreds of virulence genes. Our findings set a mechanistic paradigm for Rec-controlled histidine kinases enabling the design of virulence inhibitors.