Figure 3.

(a) E1-E2–E3 complex of Geobacillus stearothermophilus active site coupling model. Tetramers of E1 (purple) and dimers of E3 (yellow) are shown attached to the outer surface of icosahedral E2 protein (gray) formed by 60 subunits¹⁹ (reprinted from Milne, J.L. et al. Molecular structure of a 9 MDa icosahedral pyruvate dehydrogenase subcomplex containing the E2 and E3 enzymes using cryoelectron microscopy. J. Biol. Chem. 281, 4364–4370. Copyright (2006). with permission from The American Society for Biochemistry and Molecular Biology). (b) Electron micrograph of wild-type E2 protein, scale bar=50 nm²⁰ (reprinted from Dalmau, M., Lim, S., Chen, H.C., Ruiz, C. & Wang, S.W. Thermostability and molecular encapsulation within an engineered caged protein scaffold. Biotechnology and Bioengineering 101, 654–664. Copyright (2008), with permission from John Wiley and Sons).