7jth
From Proteopedia
Cryo-EM structure of unliganded octameric prenyltransferase domain of Phomopsis amygdali fusicoccadiene synthase
Structural highlights
Function[FC1_PHOAM] Multifunctional diterpene synthase; part of the 2 gene clusters that mediate the biosynthesis of fusicoccins, diterpene glucosides that display phytohormone-like activity and function as potent activators of plasma membrane H(+)-ATPases in plants by modifying 14-3-3 proteins and cause the plant disease constriction canker (PubMed:17360612, PubMed:26734760). The first step in the pathway is performed by the fusicoccadiene synthase PaFS that possesses both prenyl transferase and terpene cyclase activity, converting isopentenyl diphosphate and dimethylallyl diphosphate into geranylgeranyl diphosphate (GGDP) and successively converting GGDP into fusicocca-2,10(14)-diene, a precursor for fusicoccin H (PubMed:17360612, PubMed:26734760). Fusicoccadiene synthase is an allosteric enzyme for GGPP cyclization that generates 64% fusicoccadiene, 9% delta-araneosene, and one additional unidentified diterpene product, when incubated with GGPP (PubMed:26734760). In the absence of isopentenyl diphosphate (IPP), PaFS can also solvolyze the shorter chain geranyl diphosphate (GPP) and farnesyl diphosphate (FPP) as alternative substrates to yield predominantly acyclic products. FPP is converted to farnesol (60.5%), nerolidol (14.0%), and farnesene (14.0%), while GPP is converted to a mixture of geraniol (59.5%) and linalool (35.0%) (PubMed:26734760). The second step is the oxidation at the C-8 position by the cytochrome P450 monooxygenase PaP450-2 to yield fusicocca-2,10(14)-diene-8-beta-ol (PubMed:22870285). The cytochrome P450 monooxygenase PaP450-1 then catalyzes the hydroxylation at the C-16 position to produce fusicocca-2,10(14)-diene-8-beta,16-diol (PubMed:22870285). The dioxygenase fc-dox then catalyzes the 16-oxydation of fusicocca-2,10(14)-diene-8-beta,16-diol to yield an aldehyde (8-beta-hydroxyfusicocca-1,10(14)-dien-16-al) (PubMed:21299202, PubMed:22870285). The short-chain dehydrogenase/reductase fc-sdr catalyzes the reduction of the aldehyde to yield fusicocca-1,10(14)-diene-8-beta,16-diol (PubMed:21299202, PubMed:22870285). The next step is the hydroxylation at C-9 performed by the cytochrome P450 monooxagenase PaP450-3 that leads to fusicoccin H aglycon which is glycosylated to fusicoccin H by the O-glycosyltransferase PAGT (PubMed:22870285). Hydroxylation at C-12 by the cytochrome P450 monooxygenase PaP450-4 leads then to the production of fusicoccin Q and is followed by methylation by the O-methyltransferase PAMT to yield fusicoccin P (PubMed:22870285). Fusicoccin P is further converted to fusicoccin J via prenylation by the O-glucose prenyltransferase PaPT (PubMed:22287087). Cytochrome P450 monooxygenase PaP450-5 then performs hydroxylation at C-19 to yield dideacetyl-fusicoccin A which is acetylated to 3'-O-deacetyl-fusicoccin A by the O-acetyltransferase PaAT-2 (PubMed:22870285). Finally, a another acetylation by the O-acetyltransferase PaAT-1 yields fusicoccin A (PubMed:22870285).[1] [2] [3] [4] [5] Publication Abstract from PubMedFusicoccadiene synthase from Phomopsis amygdali (PaFS) is a unique bifunctional terpenoid synthase that catalyzes the first two steps in the biosynthesis of the diterpene glycoside Fusicoccin A, a mediator of 14-3-3 protein interactions. The prenyltransferase domain of PaFS generates geranylgeranyl diphosphate, which the cyclase domain then utilizes to generate fusicoccadiene, the tricyclic hydrocarbon skeleton of Fusicoccin A. Here, we use cryo-electron microscopy to show that the structure of full-length PaFS consists of a central octameric core of prenyltransferase domains, with the eight cyclase domains radiating outward via flexible linker segments in variable splayed-out positions. Cryo-electron microscopy and chemical crosslinking experiments additionally show that compact conformations can be achieved in which cyclase domains are more closely associated with the prenyltransferase core. This structural analysis provides a framework for understanding substrate channeling, since most of the geranylgeranyl diphosphate generated by the prenyltransferase domains remains on the enzyme for cyclization to form fusicoccadiene. Structural insight on assembly-line catalysis in terpene biosynthesis.,Faylo JL, van Eeuwen T, Kim HJ, Gorbea Colon JJ, Garcia BA, Murakami K, Christianson DW Nat Commun. 2021 Jun 9;12(1):3487. doi: 10.1038/s41467-021-23589-9. PMID:34108468[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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