Journal: Nucleic Acids Res / Year: 2025 Title: Mechanism of activation of contact-dependent growth inhibition tRNase toxin by the amino acid biogenesis factor CysK in the bacterial competition system. Authors: Zhaohang Feng / Yuka Yashiro / Kozo Tomita / Abstract: Contact-dependent growth inhibition (CDI) is a bacterial competition mechanism, wherein the C-terminal toxin domain of CdiA protein (CdiA-CT) is transferred from one bacterium to another, impeding ...Contact-dependent growth inhibition (CDI) is a bacterial competition mechanism, wherein the C-terminal toxin domain of CdiA protein (CdiA-CT) is transferred from one bacterium to another, impeding the growth of the toxin recipient. In uropathogenic Escherichia coli 536, CdiA-CT (CdiA-CTEC536) is a tRNA anticodon endonuclease that requires a cysteine biogenesis factor, CysK, for its activity. However, the mechanism underlying tRNA recognition and cleavage by CdiA-CTEC536 remains unresolved. Here, we present the cryo-EM structure of the CysK:CdiA-CTEC536:tRNA ternary complex. The interaction between CdiA-CTEC536 and CysK stabilizes the CdiA-CTEC536 structure and facilitates tRNA binding and the formation of the CdiA-CTEC536 catalytic core structure. The bottom-half of the tRNA interacts exclusively with CdiA-CTEC536 and the α-helices of CdiA-CTEC536 engage with the minor and major grooves of the bottom-half of tRNA, positioning the tRNA anticodon loop at the CdiA-CTEC536 catalytic site for tRNA cleavage. Thus, CysK serves as a platform facilitating the recognition and cleavage of substrate tRNAs by CdiA-CTEC536.
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 277.15 K / Instrument: FEI VITROBOT MARK IV
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Electron microscopy
Microscope
FEI TITAN KRIOS
Image recording
Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k) / Digitization - Dimensions - Width: 4092 pixel / Digitization - Dimensions - Height: 5760 pixel / Number grids imaged: 1 / Number real images: 7044 / Average exposure time: 1.0 sec. / Average electron dose: 50.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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