Dataset Information

Stoichiometry and architecture of the human pyruvate dehydrogenase complex.

ABSTRACT: The pyruvate dehydrogenase complex (PDHc) is a key megaenzyme linking glycolysis with the citric acid cycle. In mammalian PDHc, dihydrolipoamide acetyltransferase (E2) and the dihydrolipoamide dehydrogenase-binding protein (E3BP) form a 60-subunit core that associates with the peripheral subunits pyruvate dehydrogenase (E1) and dihydrolipoamide dehydrogenase (E3). The structure and stoichiometry of the fully assembled, mammalian PDHc or its core remained elusive. Here, we demonstrate that the human PDHc core is formed by 48 E2 copies that bind 48 E1 heterotetramers and 12 E3BP copies that bind 12 E3 homodimers. Cryo-electron microscopy, together with native and cross-linking mass spectrometry, confirmed a core model in which 8 E2 homotrimers and 12 E2-E2-E3BP heterotrimers assemble into a pseudoicosahedral particle such that the 12 E3BP molecules form six E3BP-E3BP intertrimer interfaces distributed tetrahedrally within the 60-subunit core. The even distribution of E3 subunits in the peripheral shell of PDHc guarantees maximum enzymatic activity of the megaenzyme.

SUBMITTER: Zdanowicz R

PROVIDER: S-EPMC466950 | biostudies-literature | 2024 Jul

REPOSITORIES: biostudies-literature

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Stoichiometry and architecture of the human pyruvate dehydrogenase complex.

Zdanowicz Rafal R Afanasyev Pavel P Pruška Adam A Harrison Julian A JA Giese Christoph C Boehringer Daniel D Leitner Alexander A Zenobi Renato R Glockshuber Rudi R

Science advances 20240717 29

The pyruvate dehydrogenase complex (PDHc) is a key megaenzyme linking glycolysis with the citric acid cycle. In mammalian PDHc, dihydrolipoamide acetyltransferase (E2) and the dihydrolipoamide dehydrogenase-binding protein (E3BP) form a 60-subunit core that associates with the peripheral subunits pyruvate dehydrogenase (E1) and dihydrolipoamide dehydrogenase (E3). The structure and stoichiometry of the fully assembled, mammalian PDHc or its core remained elusive. Here, we demonstrate that the hu ...[more]

PMID: 39018392

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Project description:Mammalian pyruvate dehydrogenase complex (PDC) is a key multi-enzyme assembly that is responsible for glucose homeostasis maintenance and conversion of pyruvate into acetyl-CoA. It comprises a central pentagonal dodecahedral core consisting of two subunit types (E2 and E3BP) to which peripheral enzymes (E1 and E3) bind tightly but non-covalently. Currently, there are two conflicting models of PDC (E2+E3BP) core organisation: the 'addition' model (60+12) and the 'substitution' model (48+12). Here we present the first ever low-resolution structures of human recombinant full-length PDC core (rE2/E3BP), truncated PDC core (tE2/E3BP) and native bovine heart PDC core (bE2/E3BP) obtained by small-angle X-ray scattering and small-angle neutron scattering. These structures, corroborated by negative-stain and cryo electron microscopy data, clearly reveal open pentagonal core faces, favouring the 'substitution' model of core organisation. The native and recombinant core structures are all similar to the truncated bacterial E2 core crystal structure obtained previously. Cryo-electron microscopy reconstructions of rE2/E3BP and rE2/E3BP:E3 directly confirm that the core has open pentagonal faces, agree with scattering-derived models and show density extending outwards from their surfaces, which is much more structurally ordered in the presence of E3. Additionally, analytical ultracentrifugation characterisation of rE2/E3BP, rE2 (full-length recombinant E2-only) and tE2/E3BP supports the substitution model. Superimposition of the small-angle neutron scattering tE2/E3BP and truncated bacterial E2 crystal structures demonstrates conservation of the overall pentagonal dodecahedral morphology, despite evolutionary diversity. In addition, unfolding studies using circular dichroism and tryptophan fluorescence spectroscopy show that the rE2/E3BP is less stable than its rE2 counterpart, indicative of a role for E3BP in core destabilisation. The architectural complexity and lower stability of the E2/E3BP core may be of benefit to mammals, where sophisticated fine-tuning is required for cores with optimal catalytic and regulatory efficiencies.

Dataset Information

Stoichiometry and architecture of the human pyruvate dehydrogenase complex.

Publications

Stoichiometry and architecture of the human pyruvate dehydrogenase complex.

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