Biology subjects

Tsuge, H.

Publications and source records attributed to Tsuge, H..

3 recordsLinked to original sources

bioRxiv2024

Step-by-Step Maturation Mechanism of Binary Toxin Pore Revealed by Cryo-EM Analysis

Membrane pore-forming proteins (PFPs) form ring-shaped membrane-translocating oligomers on membranes, contributing to infection, immunity, and cell death functions. Binary toxins produced by some bacteria consist of an enzymatic component that acts as a toxin and a membrane-binding component that forms a pore that delivers the enzymatic component into target cells. Cryo-electron microscopy (cryo-EM) has advanced our understanding of these translocation mechanisms by revealing several binary toxin complexes structures. However, the mechanisms underlying the initial pore formation remain unclear. We determined the structures of several oligomeric forms of the membrane-binding component Ib of the Iota toxin from Clostridium perfringens at various stages of pore formation. Structural comparisons revealed how the symmetrically arranged soluble oligomer (prepore) asymmetrically mature into a transmembrane oligomer (pore). These findings enhance our understanding of mechanisms of PFP and provide a structural basis for developing nanodevices using membrane pores. Significance StatementAlthough the mode of action of pore-forming proteins (PFPs) has been increasingly elucidated, the structural mechanisms underlying their maturation into membrane-spanning pores remain elusive. One of the key challenges is the difficulty in capturing the intermediate states between the soluble prepore and the mature pore, and its structural analysis. In this study, we successfully prepared the super-complex formed by a bacterial toxin PFP. The super-complex inhibited the constituting oligomers to maturate into the pore, which enabled structural determination of multiple intermediate state. Comparative structural analysis revealed that the transition from prepore to pore occurs through stepwise, domino-like conformational changes. The analysis workflow and insights from this study are expected to advance the field of PFP research.

molecular biology↗

bioRxiv2023

Structural elucidation and antiviral activity of cathepsin L inhibitors with carbonyl and epoxide warheads

Emerging RNA viruses including SARS-CoV-2 continue to be a major threat around the globe. The cell entry of SARS-CoV-2 particles via the endosomal pathway involves the cysteine protease cathepsin L (CatL) among other proteases. CatL is rendered as a promising drug target in the context of different viral and lysosome-related diseases. Hence, drug discovery and structure-based optimization of inhibitors is of high pharmaceutical interest. We herein verified and compared the anti-SARS-CoV-2 activity of a set of carbonyl and succinyl-epoxide-based inhibitors, which have previously been identified as cathepsin inhibitors. Calpain inhibitor XII (CI-XII), MG-101 and CatL inhibitor IV (CLI-IV) possess antiviral activity in the very low nanomolar IC50 range in Vero E6 cells. Experimental structural data on how these and related compounds bind to CatL are however notably lacking, despite their therapeutic potential. Consequently, we present and compare crystal structures of CatL in complex with 14 compounds, namely BOCA (N-BOC-2-aminoacetaldehyde), CLI-IV, CI-III, CI-VI, CI-XII, the main protease -ketoamide inhibitor 13b, MG-101, MG-132 as well as E-64d (aloxistatin), E-64, CLIK148, CAA0225, TC-I (CID 16725315) and TPCK at resolutions better than 2 [A]. Overall, the presented data comprise a broad and solid basis for structure-guided understanding and optimization of CatL inhibitors towards protease drug development.

biochemistry↗

bioRxiv2019

Translocational unfolding in clostridial binary iota toxin complex

Protein translocation across the membrane is critical for microbial pathogenesis and various cellular functions. Bacterial binary toxins such as anthrax toxin are composed of enzyme components and a translocation channel, which catalyses substrate unfolding and translocation. Here we report the structures of the clostridial binary toxin (iota toxin) translocation channel Ib-pore and its complex with ADP-ribosyltransferase Ia. The Ib-pore structure at atomic resolution provides a similar structural framework as observed for the catalytic {phi}-clamp of the anthrax protective antigen pore. However, the Ia-bound Ib-pore structure showed a unique binding mode of Ia: one Ia binds to the Ib-pore, and the Ia N-terminal domain interacts with Ib via two other Ib-pore bottlenecks with multiple weak interactions. Furthermore, Ib-binding induces Ia N-terminal -helix tilting and partial unfolding, whereupon the unfolded N-terminus continues to the {phi}-clamp gate. This study reveals the novel mechanism of N-terminal unfolding, which is crucial for protein translocation.

biophysics↗