Principles of quasi-equivalence and Euclidean geometry govern the assembly of cubic and dodecahedral cores of pyruvate dehydrogenase complexes.
The pyruvate dehydrogenase multienzyme complex (Mr of 5-10 million) is assembled around a structural core formed of multiple copies of dihydrolipoyl acetyltransferase (E2p), which exhibits the shape of either a cube or a dodecahedron, depending on the source. The crystal structures of the 60-meric dihydrolipoyl acyltransferase cores of Bacillus stearothermophilus and Enterococcus faecalis pyruvate dehydrogenase complexes were determined and revealed a remarkably hollow dodecahedron with an outer diameter of approximately 237 A, 12 large openings of approximately 52 A diameter across the fivefold axes, and an inner cavity with a diameter of approximately 118 A. Comparison of cubic and dodecahedral E2p assemblies shows that combining the principles of quasi-equivalence formulated by Caspar and Klug [Caspar, D. L. & Klug, A. (1962) Cold Spring Harbor Symp. Quant. Biol. 27, 1-4] with strict Euclidean geometric considerations results in predictions of the major features of the E2p dodecahedron matching the observed features almost exactly.
Izard
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Departments of Biological Structure and Biochemistry, Biomolecular Structure Center, and Howard Hughes Medical Institute, University of Washington, Box 357742, Seattle, WA 98195-7742, USA.
Aevarsson
A
A
Allen
M D
MD
Westphal
A H
AH
Perham
R N
RN
de Kok
A
A
Hol
W G
WG
D000123:Acetyltransferases / Q000737:chemistry*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D013293:Enterococcus faecalis / Q000201:enzymology*; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D046911:Macromolecular Substances; D008433:Mathematics; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011768:Pyruvate Dehydrogenase Complex / Q000737:chemistry*; D012984:Software