UbiX is a flavin prenyltransferase required for bacterial ubiquinone biosynthesis

Abstract

Ubiquinone, or coenzyme Q, is a ubiquitous lipid-soluble redox cofactor that is an essential component of electron transfer chains1. Eleven genes have been implicated in bacterial ubiquinone biosynthesis, including ubiX and ubiD, which are responsible for decarboxylation of the 3-octaprenyl-4-hydroxybenzoate precursor2. Despite structural and biochemical characterization of UbiX as an FMN-binding protein, no decarboxylase activity has been detected3–4. We report here that UbiX produces a novel flavin-derived cofactor required for the decarboxylase activity of UbiD5. UbiX acts as a flavin prenyltransferase, linking a dimethylallyl moiety to the flavin N5 and C6 atoms. This adds a fourth non-aromatic ring to the flavin isoalloxazine group. In contrast to other prenyltransferases6–7, UbiX is metal-independent and requires dimethylallyl-monophosphate as substrate. Kinetic crystallography reveals that the prenyl transferase mechanism of UbiX resembles that of the terpene synthases8. The active site environment is dominated by π-systems, which assist phosphate-C1’ bond breakage following FMN reduction, leading to formation of the N5-C1’ bond. UbiX then acts as a chaperone for adduct reorientation, via transient carbocation species, leading ultimately to formation of the dimethylallyl C3’-C6 bond. The study establishes the mechanism for formation of a new flavin-derived cofactor, extending both flavin and terpenoid biochemical repertoire.

Requirement of a Functional Flavin Mononucleotide Prenyltransferase for the Activity of a Bacterial Decarboxylase in a Heterologous Muconic Acid Pathway in Saccharomyces cerevisiae

“…Recently, it has been demonstrated that Fdc1 and its bacterial homologue UbiD perform the actual decarboxylase function, whereas Pad1 and its bacterial homologue UbiX are responsible for the prenylation of flavin mononucleotide (FMN), leading to the generation of a cofactor required for decarboxylase function (13,27,28). In contrast to Fdc1/Pad1, UbiD/UbiX is involved in the biosynthesis of ubiquinone in E. coli.…”

Prenyltransferases as key enzymes in primary and secondary metabolism

“…Very recently, a prenyltransferase UbiX from P. aeruginosa involved in the biosynthesis of ubiquinones was demonstrated to use flavin as a prenyl acceptor. In contrast to prenyl diphosphates for other known prenyltransferases, dimethylallyl monophosphate (DMAP) serves as prenyl donor for UbiX reaction (White et al 2015).…”

Plastoquinone and Ubiquinone in Plants: Biosynthesis, Physiological Function and Metabolic Engineering

“…It has been shown that ubiX and ubiD genes are involved in the decarboxylation of UQ aromatic ring in bacteria (Meganathan, 2001; Gulmezian et al, 2007; Aussel et al, 2014). ubiX encodes a flavin mononucleotide (FMN)-binding protein with no decarboxylase activity detected in vitro (Gulmezian et al, 2007; Aussel et al, 2014), and UbiX proteins are metal-independent and require dimethylallyl-monophosphate as substrate (White et al, 2015). During the biosynthesis of UQ, UbiX acts as a flavin PT, producing a flavin-derived cofactor required for the decarboxylase activity of UbiD (Payne et al, 2015; White et al, 2015).…”

“…ubiX encodes a flavin mononucleotide (FMN)-binding protein with no decarboxylase activity detected in vitro (Gulmezian et al, 2007; Aussel et al, 2014), and UbiX proteins are metal-independent and require dimethylallyl-monophosphate as substrate (White et al, 2015). During the biosynthesis of UQ, UbiX acts as a flavin PT, producing a flavin-derived cofactor required for the decarboxylase activity of UbiD (Payne et al, 2015; White et al, 2015). pad1 and fdc1 are two fungal genes related to bacterial ubiX and ubiD (Mukai et al, 2010; Lin et al, 2015; Payne et al, 2015).…”