3el3
Distinct Monooxygenase and Farnesene Synthase Active Sites in Cytochrome P450 170A1
Structural highlights
FunctionEIZFM_STRCO Involved in the biosynthesis of the sesquiterpenoid antibiotic albaflavenone. Catalyzes the two-step allylic oxidation of epi-isozizaene to albaflavenone. First carries out a non-stereo-specific oxidation of epi-isozizaene to give a mixture of the albaflavenol epimers ((5R)-albaflavenol and (5S)-albaflavenol), each of which can serve as substrate for the second oxidation to yield albaflavenone. This is quite different from most other P450s which catalyze regio- and stereospecific oxidation. Displays also a farnesene synthase activity with farnesyl diphosphate (FPP) as substrate.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAlbaflavenone synthase (CYP170A1) is a monooxygenase catalyzing the final two steps in the biosynthesis of this antibiotic in the soil bacterium, Streptomyces coelicolor A3(2). Interestingly, CYP170A1 shows no stereo selection forming equal amounts of two albaflavenol epimers, each of which is oxidized in turn to albaflavenone. To explore the structural basis of the reaction mechanism, we have studied the crystal structures of both ligand-free CYP170A1 (2.6 A) and complex of endogenous substrate (epi-isozizaene) with CYP170A1 (3.3 A). The structure of the complex suggests that the proximal epi-isozizaene molecules may bind to the heme iron in two orientations. In addition, much to our surprise, we have found that albaflavenone synthase also has a second, completely distinct catalytic activity corresponding to the synthesis of farnesene isomers from farnesyl diphosphate. Within the cytochrome P450 alpha-helical domain both the primary sequence and x-ray structure indicate the presence of a novel terpene synthase active site that is moonlighting on the P450 structure. This includes signature sequences for divalent cation binding and an alpha-helical barrel. This barrel is unusual because it consists of only four helices rather than six found in all other terpene synthases. Mutagenesis establishes that this barrel is essential for the terpene synthase activity of CYP170A1 but not for the monooxygenase activity. This is the first bifunctional P450 discovered to have another active site moonlighting on it and the first time a terpene synthase active site is found moonlighting on another protein. Crystal structure of albaflavenone monooxygenase containing a moonlighting terpene synthase active site.,Zhao B, Lei L, Vassylyev DG, Lin X, Cane DE, Kelly SL, Yuan H, Lamb DC, Waterman MR J Biol Chem. 2009 Dec 25;284(52):36711-9. Epub 2009 Oct 26. PMID:19858213[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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