cell envelope organization / cell wall biogenesis / cell envelope / protein secretion by the type III secretion system / outer membrane-bounded periplasmic space / endopeptidase activity / periplasmic space / serine-type endopeptidase activity / signal transduction / proteolysis / plasma membrane Similarity search - Function
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
AI136901
United States
Citation
Journal: EMBO J / Year: 2024 Title: P. aeruginosa CtpA protease adopts a novel activation mechanism to initiate the proteolytic process. Authors: Hao-Chi Hsu / Michelle Wang / Amanda Kovach / Andrew J Darwin / Huilin Li / Abstract: During bacterial cell growth, hydrolases cleave peptide cross-links between strands of the peptidoglycan sacculus to allow new strand insertion. The Pseudomonas aeruginosa carboxyl-terminal ...During bacterial cell growth, hydrolases cleave peptide cross-links between strands of the peptidoglycan sacculus to allow new strand insertion. The Pseudomonas aeruginosa carboxyl-terminal processing protease (CTP) CtpA regulates some of these hydrolases by degrading them. CtpA assembles as an inactive hexamer composed of a trimer-of-dimers, but its lipoprotein binding partner LbcA activates CtpA by an unknown mechanism. Here, we report the cryo-EM structures of the CtpA-LbcA complex. LbcA has an N-terminal adaptor domain that binds to CtpA, and a C-terminal superhelical tetratricopeptide repeat domain. One LbcA molecule attaches to each of the three vertices of a CtpA hexamer. LbcA triggers relocation of the CtpA PDZ domain, remodeling of the substrate binding pocket, and realignment of the catalytic residues. Surprisingly, only one CtpA molecule in a CtpA dimer is activated upon LbcA binding. Also, a long loop from one CtpA dimer inserts into a neighboring dimer to facilitate the proteolytic activity. This work has revealed an activation mechanism for a bacterial CTP that is strikingly different from other CTPs that have been characterized structurally.
Model: Quantifoil R1.2/1.3 / Material: GOLD / Mesh: 300 / Support film - Material: CARBON / Support film - topology: HOLEY / Pretreatment - Type: PLASMA CLEANING / Pretreatment - Time: 30 sec. / Pretreatment - Atmosphere: OTHER
Vitrification
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 279 K / Instrument: FEI VITROBOT MARK IV
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Electron microscopy
Microscope
FEI TITAN KRIOS
Specialist optics
Energy filter - Name: GIF Bioquantum / Energy filter - Slit width: 20 eV
Image recording
Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k) / Digitization - Dimensions - Width: 11520 pixel / Digitization - Dimensions - Height: 8184 pixel / Number grids imaged: 1 / Number real images: 26257 / Average exposure time: 1.5 sec. / Average electron dose: 66.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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