Fig. 10. Proposed gating mechanism of elongating ketosynthases.

Figure demonstrates the active site conformational changes that facilitate acyl-chain transfer in elongating KSs as demonstrated by trapped crystallographic states from this work and previous studies. a The apo-form of the KS active site illustrated by a 2D schematic of the active site architecture (top) and the crystal structure of apo-FabF (PDB: 2GFW) (bottom). b Active site reorganization to the gate-open conformation upon association of acyl-AcpP with KSs as seen in the C16AcpP–FabF structure reported herein with a 2D schematic of the active site (top) and 3D rendering of the active site (bottom). c Active site of C12AcpP–FabB, illustrating the gate-closed transacylation competent form of the active sites of elongating KSs shown as 2D schematic (top) and 3D rendering (bottom). Residues are represented in FabF numbering. d The acyl-enzyme adduct form of FabF (PDB: 2GFY) shown as a 2D schematic (top) and 3D rendering (bottom). Active site catalytic residues Cys163, His303, His340, and Phe400 are provided in FabF residue numbering, represented as sticks, and colored according to element (C-white, O-red, N-blue, S-yellow). Hydrogen-bonding interactions are represented as dotted lines.