Netherlands Organisation for Scientific Research (NWO)
Netherlands
Citation
Journal: Commun Biol / Year: 2024 Title: Membrane-embedded CdaA is required for efficient synthesis of second messenger cyclic di-AMP. Authors: Alexander J Foster / Haoyang Li / Panagiotis Drougkas / Gea K Schuurman-Wolters / Joeri Ten Kate / Cristina Paulino / Bert Poolman / Abstract: Cyclic di-adenylate monophosphate (cyclic di-AMP) is an important second messenger in microorganisms. Cyclic di-AMP regulates bacterial cell volume and turgor via control of potassium and compatible ...Cyclic di-adenylate monophosphate (cyclic di-AMP) is an important second messenger in microorganisms. Cyclic di-AMP regulates bacterial cell volume and turgor via control of potassium and compatible solute transport but is also involved in many other processes, including the activation of the metazoan innate immune response to bacterial infections. We compare the activity of full-length membrane-embedded CdaA, the enzyme that synthesizes cyclic di-AMP, with the water-soluble catalytic domain CdaA-DAC. Purified CdaA from L. lactis was studied in the detergent-solubilized state, and in lipid nanodiscs and vesicles. We show that CdaA is tetrameric and the membrane-bound complex has more than 2-orders of magnitude higher activity than soluble CdaA-DAC. CdaA activity increases with pH but does not strongly depend on the salt or lipid content, factors that are crucial for the control of osmoregulatory transporters. Cryo-EM and in-silico structure prediction of CdaA show that the two DAC dimers engage in a head-to-head interaction, leading to cyclic-di-AMP formation. The inhibitor phosphoglucomutase prevents this active conformation. We observe dynamic flexibility between the catalytic and membrane domains, even in the presence of ATP or non-hydrolyzable substrate ApCpp. This is the first comprehensive functional and structural characterization of a full-length cyclic di-AMP-specific cyclase.
Model: Quantifoil R1.2/1.3 / Material: GOLD / Mesh: 300 / Support film - Material: CARBON / Support film - topology: HOLEY / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 20 sec. / Details: 5 mA
Vitrification
Cryogen name: ETHANE-PROPANE / Chamber humidity: 100 % / Chamber temperature: 293 K / Instrument: FEI VITROBOT MARK IV Details: 13.2 uM of GlmM and 10 mM of Mn-ATP were added prior to sample application onto the grids. Grids were blotted for 4 seconds..
Details
Full-length CdaA
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Electron microscopy
Microscope
FEI TALOS ARCTICA
Temperature
Min: 90.0 K / Max: 105.0 K
Specialist optics
Energy filter - Name: GIF Bioquantum / Energy filter - Slit width: 20 eV
Image recording
Film or detector model: GATAN K2 SUMMIT (4k x 4k) / Detector mode: COUNTING / Digitization - Dimensions - Width: 3838 pixel / Digitization - Dimensions - Height: 3710 pixel / Digitization - Frames/image: 1-60 / Number grids imaged: 1 / Number real images: 5150 / Average exposure time: 9.0 sec. / Average electron dose: 53.6 e/Å2
Electron beam
Acceleration voltage: 200 kV / Electron source: FIELD EMISSION GUN
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