Fig. 5: The interdomain active site within the bovine PDC E2 IC domain trimers.

a Ribbon-model of E2p trimer (colored by subunits) with boxes highlighting the relative locations of the flexible βE–βF turn (black box). b Enlarged views of the βE–βF turn near interdomain active site relative to conserved catalytic residues (teal), Ser566 from the red subunit and His620 and Asp624 from the green subunit. Two residues (Ala519 and Gly520) are unmodeled in the turn due to absence of continuous cryo-EM density (semi-transparent gray; for clarity, only those for βE–turn–βF are shown), suggesting flexibility of the residues in the turn. The conserved leucine gatekeeper (orange) is next to these unmodeled residues. A weak density (pink) bordered by catalytic and gatekeeper residues within active site is visible. c Cryo-EM density of the same region of b shown at a decreased threshold as semi-transparent pink for the lipoyl moiety or gray for the surrounding region. Atomic models for the lipoyl moiety (from PDB ID: 1EAE) and the surrounding area are shown as sticks and ribbon, respectively.