National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
AI175342
United States
Citation
Journal: J Biol Chem / Year: 2026 Title: Mycobacterium tuberculosis assembles a unique hexameric E2p core of the pyruvate dehydrogenase complex. Authors: Hao-Chi Hsu / Isabelle Bonnet / Ruslana Bryk / Huilin Li / Abstract: The pyruvate dehydrogenase complex (PDHc) is a universally conserved multienzyme system that converts pyruvate into acetyl-CoA for entry into the TCA cycle and for NADH production. Its central ...The pyruvate dehydrogenase complex (PDHc) is a universally conserved multienzyme system that converts pyruvate into acetyl-CoA for entry into the TCA cycle and for NADH production. Its central scaffold, the dihydrolipoyl transacetylase (E2p), forms an oligomeric inner core that recruits pyruvate dehydrogenase (E1p) and dihydrolipoyl dehydrogenase (E3). All previously characterized PDHc assemblies adopt either an octahedral 24-mer or an icosahedral 60-mer E2p core, each constructed from trimeric building blocks. We recently showed that the Mycobacterium tuberculosis (Mtb) E2p protein DlaT also functions as the core of the pathogen's peroxynitrite reductase/peroxidase (PNR/P) complex. Here, using cryo-EM, we demonstrate that DlaT assembles into discrete hexamers and dodecamers at micromolar concentrations, which approximate intracellular DlaT concentrations in Mtb. Structure-guided mutagenesis combined with in vitro activity assays indicate that the hexamer represents the functional E2p core of the Mtb PDHc. This noncanonical architecture arises from unique interfaces between DlaT trimers that preclude formation of the classic spherical 24- or 60-mer structures. We propose that this specialized E2p organization enables Mtb to regulate metabolic activities and to remodel the E2p core for engagement in the PNR/P antioxidant pathway under stress. Our findings reveal an unexpected diversity in PDHc architecture and uncover a distinct organization principle for the core metabolic complex in mycobacteria.
UniProtKB: Dihydrolipoyllysine-residue acetyltransferase component of pyruvate dehydrogenase complex
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Experimental details
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Structure determination
Method
cryo EM
Processing
single particle reconstruction
Aggregation state
particle
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Sample preparation
Concentration
1.2 mg/mL
Buffer
pH: 7.5 / Details: 20 mM Tris, pH 7.5, 5 mM MgCl2, and 100 mM KCl
Grid
Model: Quantifoil R1.2/1.3 / Material: GOLD / Mesh: 300 / Support film - Material: CARBON / Support film - topology: HOLEY ARRAY / Support film - Film thickness: 10 / Pretreatment - Type: GLOW DISCHARGE / 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 TALOS ARCTICA
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: 5760 pixel / Digitization - Dimensions - Height: 4092 pixel / Number grids imaged: 1 / Number real images: 3144 / Average exposure time: 1.4 sec. / Average electron dose: 55.0 e/Å2
Electron beam
Acceleration voltage: 200 kV / Electron source: FIELD EMISSION GUN
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