This is Figure 15.5b from Lehninger, A.L.; Nelson, D.L.; Cox, M.M. Principles of Biochemistry; Worth: New York, 1993; page 450.

This figure shows the arrangement of the E1, E2 and E3 subumits of mammalian pyruvate dehydrogenase complex.

• The green cluster of spheres on the interior of the cubic arrangement are the 24 E2 (dihydrolipoamide acetyltransferase) catalytic domains. The red spheres projecting out from these are the lipoyllysyl domains of the E2s.
• The orange spheres on the "edges" of the cube represent the 24 dimeric E1s (pyruvate dehydrogenase).
• The yellow spheres in the center of the "cube face" represent the 6 dimeric E3s (dihydrolipoamide dehydrogenase).