Summary Cytochromes P450 (CYPs) play key role in generating the structural diversity of terpenoids, the largest group of plant natural products. However, functional characterization of CYPs has been challenging because of the expansive families found in plant genomes, diverse reactivity and inaccessibility of their substrates and products.Here we present the characterization of two CYPs, CYP76AH3 and CYP76AK1, that act sequentially to form a bifurcating pathway for the biosynthesis of tanshinones, the oxygenated diterpenoids from the Chinese medicinal plant Danshen.These CYPs had similar transcription profiles to that of the known gene responsible for tanshinone production in elicited Danshen hairy roots. Biochemical and RNA interference studies demonstrated that both CYPs are promiscuous. CYP76AH3 oxidizes ferruginol at two different carbon centers, and CYP76AK1 hydroxylates C-20 of two of the resulting intermediates. Together, these convert ferruginol into 11,20-dihydroxy ferruginol and 11,20-dihydroxy sugiol en route to tanshinones. Moreover, we demonstrate the utility of these CYPs by engineering yeast for heterologous production of six oxygenated diterpenoids, which in turn enabled structural characterization of three novel compounds produced by CYP-mediated oxidation.Our results highlight the incorporation of multiple CYPs in diterpenoids metabolic engineering, and a continuing trend of CYPs promiscuity generating complex networks in terpenoid biosynthesis.

Homology modeling has been applied to fill in the gap in experimental G protein-coupled receptors structure determination. However, achievement of G protein-coupled receptors homology models with ligand selectivity remains challenging due to structural diversity of G protein-coupled receptors. In this work, we propose a novel strategy by integrating pharmacophore and membrane molecular dynamics (MD) simulations to improve homology modeling of G protein-coupled receptors with ligand selectivity. To validate this integrated strategy, the A2A adenosine receptor (A2A AR), whose structures in both active and inactive states have been established, has been chosen as an example. We performed blind predictions of the active-state A2A AR structure based on the inactive-state structure and compared the performance of different refinement strategies. The blind prediction model combined with the integrated strategy identified ligand-receptor interactions and conformational changes of key structural elements related to the activation of A2 A AR, including (i) the movements of intracellular ends of TM3 and TM5/TM6; (ii) the opening of ionic lock; (iii) the movements of binding site residues. The integrated strategy of pharmacophore with molecular dynamics simulations can aid in the optimization in the identification of side chain conformations in receptor models. This strategy can be further investigated in homology modeling and expand its applicability to other G protein-coupled receptor modeling, which should aid in the discovery of more effective and selective G protein-coupled receptor ligands.