Mitoquinone Inactivates Mitochondrial Chaperone TRAP1 by Blocking the Client Binding Site.

Heat shock protein 90 (Hsp90) family proteins are molecular chaperones that modulate the functions of various substrate proteins (clients) implicated in pro-tumorigenic pathways. In this study, the mitochondria-targeted antioxidant mitoquinone (MitoQ) was identified as a potent inhibitor of mitochondrial Hsp90, known as a tumor necrosis factor receptor-associated protein 1 (TRAP1). Structural analyses revealed an asymmetric bipartite interaction between MitoQ and the previously unrecognized drug binding sites located in the middle domain of TRAP1, believed to be a client binding region. MitoQ effectively competed with TRAP1 clients, and MitoQ treatment facilitated the identification of 103 TRAP1-interacting mitochondrial proteins in cancer cells. MitoQ and its redox-crippled SB-U014/SB-U015 exhibited more potent anticancer activity in vitro and in vivo than previously reported mitochondria-targeted TRAP1 inhibitors. The findings indicate that targeting the client binding site of Hsp90 family proteins offers a novel strategy for the development of potent anticancer drugs.

Structure-guided synthesis of a protein-based fluorescent sensor for alkyl halides.

Alkyl halides are potentially mutagenic carcinogens. However, no efficient fluorescent sensor for alkyl halide detection in human-derived samples has been developed to date. Herein, we report a new protein-based fluorescent sensor for alkyl halides. Analysis of the HaloTag holo-crystal structure with its covalently attached ligand revealed an unexpected cavity, allowing for the design of a new fluorogenic ligand. This ligand showed the highest fluorescence response (300-fold) and fastest binding kinetics (t1/2 < 150 s) to a HaloTag mutant (M175P) protein. This protein-based sensor system was effectively used to detect alkyl halides in human serum and monitor real-time protein alkylation.