Structure-function analysis of PvCPS3 and PvCPS1. Homology models are shown for PvCPS3 (top) and PvCPS1 (bottom) with GGPP docked into the class II active site situated at the γ-domain (orange) and β-domain (teal) interface. Models were generated using the crystal structure of Arabidopsis ent-CPS (Protein Data Bank code 4LIX) as a template (Köksal et al., 2014). Residues targeted for site-directed mutagenesis in this study are indicated. Reaction products resulting from E. coli coexpression assays of the wild type and mutant variants of PvCPS3 and PvCPS1 are highlighted as labdane (orange), hydroxylated labdane (pink), and clerodane (blue) scaffolds and numbered as follows: 11, 8,13-CPP; 12, ent-neo-CT-CLPP; 14, 7,13-CPP; 15, (+)-CPP; 16, (+)-8β-LPP; 17, (+)-8α-LPP; 18, syn-halima-5,13E-dienyl diphosphate (5,13-HPP). Corresponding GC-MS chromatograms and mass spectra are given in Supplemental Figure S4.