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https://hdl.handle.net/2440/69054
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Type: | Journal article |
Title: | Variation in the organization and subunit composition of the mammalian pyruvate dehydrogenase complex E2/E3BP core assembly |
Author: | Vijayakrishnan, S. Callow, P. Nutley, M. McGow, D. Gilbert, D. Kropholler, P. Cooper, A. Byron, O. Lindsay, J. |
Citation: | Biochemical Journal, 2011; 437(3):565-574 |
Publisher: | Biochemical Society |
Issue Date: | 2011 |
ISSN: | 0264-6021 1470-8728 |
Statement of Responsibility: | Swetha Vijayakrishnan, Philip Callow, Margaret A. Nutley, Donna P. McGow, David Gilbert, Peter Kropholler, Alan Cooper, Olwyn Byron and J. Gordon Lindsay |
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. |
Keywords: | E3-binding stoichiometry E2/E3BP core organization isothermal titration calorimetry (ITC) pyruvate dehydrogenase complex small-angle neutron scattering (SANS) variable substitution model |
Rights: | Copyright The Authors Journal compilation Copyright 2011 Biochemical Society |
DOI: | 10.1042/bj20101784 |
Published version: | http://dx.doi.org/10.1042/bj20101784 |
Appears in Collections: | Aurora harvest 5 Environment Institute Leaders publications IPAS publications |
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