National Institutes of Health/National Center for Research Resources (NIH/NCRR)
U24GM129547
United States
National Institutes of Health/National Center for Research Resources (NIH/NCRR)
S10OD02509
United States
Brazilian National Council for Scientific and Technological Development (CNPq)
232251/2014-2
Brazil
Brazilian National Council for Scientific and Technological Development (CNPq)
140636/2013-7
Brazil
Citation
Journal: Curr Res Struct Biol / Year: 2024 Title: Bacterial selenocysteine synthase structure revealed by single-particle cryoEM. Authors: Vitor Hugo Balasco Serrão / Karine Minari / Humberto D'Muniz Pereira / Otavio Henrique Thiemann / Abstract: The 21st amino acid, selenocysteine (Sec), is synthesized on its dedicated transfer RNA (tRNA). In bacteria, Sec is synthesized from Ser-tRNA by Selenocysteine Synthase (SelA), which is a pivotal ...The 21st amino acid, selenocysteine (Sec), is synthesized on its dedicated transfer RNA (tRNA). In bacteria, Sec is synthesized from Ser-tRNA by Selenocysteine Synthase (SelA), which is a pivotal enzyme in the biosynthesis of Sec. The structural characterization of bacterial SelA is of paramount importance to decipher its catalytic mechanism and its role in the regulation of the Sec-synthesis pathway. Here, we present a comprehensive single-particle cryo-electron microscopy (SPA cryoEM) structure of the bacterial SelA with an overall resolution of 2.69 Å. Using recombinant SelA, we purified and prepared samples for single-particle cryoEM. The structural insights from SelA, combined with previous and knowledge, underscore the indispensable role of decamerization in SelA's function. Moreover, our structural analysis corroborates previous results that show that SelA adopts a pentamer of dimers configuration, and the active site architecture, substrate binding pocket, and key K295 catalytic residue are identified and described in detail. The differences in protein architecture and substrate coordination between the bacterial enzyme and its counterparts offer compelling structural evidence supporting the independent molecular evolution of the bacterial and archaea/eukarya Ser-Sec biosynthesis present in the natural world.
Details: 20 mM potassium phosphate pH 7.5, 100 mM sodium chloride, 2 mM 2-mercaptoethanol, and 10 uM pyridoxal 5-phosphate.
Grid
Model: Quantifoil / Material: COPPER / Mesh: 400 / Support film - Material: CARBON / Support film - topology: HOLEY ARRAY / Support film - Film thickness: 20 / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 20 sec. / Pretreatment - Pressure: 0.00035999999999999997 kPa
Vitrification
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 295 K / Instrument: FEI VITROBOT MARK IV Details: The sample was blotted for 2.5 seconds using a force of -10 and then swiftly plunged frozen into liquid ethane using the Vitrobot Mark IV - Thermo Fisher Scientific..
Details
Monodisperse sample after size-exclusion chromatography
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Electron microscopy
Microscope
FEI TITAN KRIOS
Image recording
Film or detector model: FEI FALCON IV (4k x 4k) / Number grids imaged: 1 / Number real images: 4592 / Average electron dose: 45.4 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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