Figure 5. Structure-based mechanism of epoxidation.
Three different views of the disposition of atoms in the O2-scission site are shown in A, B and C to emphasize orientation of the to-be-epoxidized double bond C4-C5 and position of W2168 (red sphere) with respect to each other and the heme iron. A clipped fragment of 4,5-desepoxypimaricin accommodating the reaction site is shown in yellow with oxygen atoms in red and hydrogen atoms in grey. Ala234 is shown with carbon atoms in grey. Blue arrow points are collinear with the C4-C5 π-orbitals. Fragment of the I-helix is shown as a grey ribbon. Distances are in Angstroms. In red are the distances between W2168 and the C4 or C5 carbons. D, Epoxidation reaction scheme. Substrate atoms are outlined in grey.