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Variation in the organization and subunit composition of the mammalian pyruvate dehydrogenase complex E2/E3BP core assembly

Variation in the organization and subunit composition of the mammalian pyruvate dehydrogenase complex E2/E3BP core assembly
Variation in the organization and subunit composition of the mammalian pyruvate dehydrogenase complex E2/E3BP core assembly
Crucial to glucose homoeostasis in humans, the hPDC (human pyruvate dehydrogenase complex) is a massive molecular machine comprising multiple copies of three distinct enzymes (E1-E3) and an accessory subunit, E3BP (E3-binding protein). Its icosahedral E2/E3BP 60-meric 'core' provides the central structural and mechanistic framework ensuring favourable E1 and E3 positioning and enzyme co-operativity. Current core models indicate either a 48E2+12E3BP or a 40E2+20E3BP subunit composition. In the present study, we demonstrate clear differences in subunit content and organization between the recombinant hPDC core (rhPDC; 40E2+20E3BP), generated under defined conditions where E3BP is produced in excess, and its native bovine (48E2+12E3BP) counterpart. The results of the present study provide a rational basis for resolving apparent differences between previous models, both obtained using rhE2/E3BP core assemblies where no account was taken of relative E2 and E3BP expression levels. Mathematical modelling predicts that an 'average' 48E2+12E3BP core arrangement allows maximum flexibility in assembly, while providing the appropriate balance of bound E1 and E3 enzymes for optimal catalytic efficiency and regulatory fine-tuning. We also show that the rhE2/E3BP and bovine E2/E3BP cores bind E3s with a 2:1 stoichiometry, and propose that mammalian PDC comprises a heterogeneous population of assemblies incorporating a network of E3 (and possibly E1) cross-bridges above the core surface.
E3-binding stoichiometry, E2/E3BP core organization, isothermal titration calorimetry (ITC), pyruvate dehydrogenase complex, small-angle neutron scattering (SANS), variable substitution model.
1470-8728
565-574
Vijayakrishnan, Swetha
fc7b4d7c-e148-422a-b35b-3a5238eb1074
Callow, Philip
d43c9b90-d993-43d6-9c74-2a18f3c8b519
Nutley, Margaret A.
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McGow, Donna P.
cfe35042-a4f1-4aac-bc54-d6d995bc5af0
Gilbert, David
7ad07aaf-7624-4020-a240-e2556b451cbe
Kropholler, Peter
0a2b4a66-9f0d-4c52-8541-3e4b2214b9f4
Cooper, Alan
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Byron, Olwyn
b9c7d9e0-a745-47cc-bc54-2c42c19081f3
Lindsay, J. Gordon
a8081f8f-2ea9-4636-9bbd-d8ef2906c10a
Vijayakrishnan, Swetha
fc7b4d7c-e148-422a-b35b-3a5238eb1074
Callow, Philip
d43c9b90-d993-43d6-9c74-2a18f3c8b519
Nutley, Margaret A.
7a835a72-d8c8-40de-8780-66f3bb123fb4
McGow, Donna P.
cfe35042-a4f1-4aac-bc54-d6d995bc5af0
Gilbert, David
7ad07aaf-7624-4020-a240-e2556b451cbe
Kropholler, Peter
0a2b4a66-9f0d-4c52-8541-3e4b2214b9f4
Cooper, Alan
9971af32-4b24-4794-b5b1-e4c78965e191
Byron, Olwyn
b9c7d9e0-a745-47cc-bc54-2c42c19081f3
Lindsay, J. Gordon
a8081f8f-2ea9-4636-9bbd-d8ef2906c10a

Vijayakrishnan, Swetha, Callow, Philip, Nutley, Margaret A., McGow, Donna P., Gilbert, David, Kropholler, Peter, Cooper, Alan, Byron, Olwyn and Lindsay, J. Gordon (2011) Variation in the organization and subunit composition of the mammalian pyruvate dehydrogenase complex E2/E3BP core assembly. Biochemical Journal, 437 (3), 565-574. (doi:10.1042/BJ20101784). (PMID:21627584)

Record type: Article

Abstract

Crucial to glucose homoeostasis in humans, the hPDC (human pyruvate dehydrogenase complex) is a massive molecular machine comprising multiple copies of three distinct enzymes (E1-E3) and an accessory subunit, E3BP (E3-binding protein). Its icosahedral E2/E3BP 60-meric 'core' provides the central structural and mechanistic framework ensuring favourable E1 and E3 positioning and enzyme co-operativity. Current core models indicate either a 48E2+12E3BP or a 40E2+20E3BP subunit composition. In the present study, we demonstrate clear differences in subunit content and organization between the recombinant hPDC core (rhPDC; 40E2+20E3BP), generated under defined conditions where E3BP is produced in excess, and its native bovine (48E2+12E3BP) counterpart. The results of the present study provide a rational basis for resolving apparent differences between previous models, both obtained using rhE2/E3BP core assemblies where no account was taken of relative E2 and E3BP expression levels. Mathematical modelling predicts that an 'average' 48E2+12E3BP core arrangement allows maximum flexibility in assembly, while providing the appropriate balance of bound E1 and E3 enzymes for optimal catalytic efficiency and regulatory fine-tuning. We also show that the rhE2/E3BP and bovine E2/E3BP cores bind E3s with a 2:1 stoichiometry, and propose that mammalian PDC comprises a heterogeneous population of assemblies incorporating a network of E3 (and possibly E1) cross-bridges above the core surface.

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More information

Published date: 1 August 2011
Keywords: E3-binding stoichiometry, E2/E3BP core organization, isothermal titration calorimetry (ITC), pyruvate dehydrogenase complex, small-angle neutron scattering (SANS), variable substitution model.
Organisations: Mathematical Sciences, Bioengineering Group

Identifiers

Local EPrints ID: 350374
URI: https://eprints.soton.ac.uk/id/eprint/350374
ISSN: 1470-8728
PURE UUID: 9a9fd2af-879c-4b6a-bb44-7e8f8420fee3

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Date deposited: 22 Mar 2013 11:55
Last modified: 18 Jul 2017 04:35

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