The key to unlock the Hsp100/Clp protein degradation machines ofMycobacterium

Structural Insights into Bortezomib-Induced Activation of the Caseinolytic Chaperone-Protease System in Mycobacterium tuberculosis

The caseinolytic protease (Clp) system has recently emerged as a promising anti-tuberculosis target. The anti-cancer drug bortezomib exhibits potent anti-mycobacterial activity and binds to Mycobacterium tuberculosis (Mtb) Clp protease complexes. We determine cryo-EM structures of Mtb ClpP1P2, ClpC1P1P2 and ClpXP1P2 complexes bound to bortezomib in different conformations. Structural and biochemical data indicate that sub-stoichiometric binding by bortezomib to the protease active sites orthosterically activates the MtbClpP1P2 complex. Bortezomib activation of MtbClpP1P2 induces structural changes promoting the recruitment of the chaperone-unfoldases, MtbClpC1 or MtbClpX, facilitating holoenzyme formation. The structures of the MtbClpC1P1P2 holoenzyme indicate that MtbClpC1 motion, induced by ATP rebinding at the MtbClpC1 spiral seam, translocates the substrate. In the MtbClpXP1P2 holoenzyme structure, we identify a specialized substrate channel gating mechanism involving the MtbClpX pore-2 loop and MtbClpP2 N-terminal domains. Our results provide insights into the intricate regulation of the Mtb Clp system and suggest that bortezomib can disrupt this regulation by sub-stoichiometric binding at the Mtb Clp protease sites.

Exploring a potential Achilles heel of Mycobacterium tuberculosis: defining the ClpC1 interactome

Protein degradation plays a vital role in the correct maintenance of a cell, not only under normal physiological conditions but also in response to stress. In the human pathogen Mtb, this crucial cellular task is performed by several ATPase associated with diverse cellular activities proteases including ClpC1P. Ziemski et al. performed a bacterial adenylate cyclase two-hybrid screen to identify ClpC1 substrates and showed the Type II TA systems represent a major group of ClpC1-interacting proteins. Comment on: https://doi.org/10.1111/febs.15335.