6 Papers found (0.008 seconds)

Salinas G et al. (2020) Biochim Biophys Acta Bioenerg "Rhodoquinone in bacteria and animals: two distinct pathways for biosynthesis of this key electron transporter used in anaerobic bioenergetics."

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Biochim Biophys Acta Bioenerg,

2020]

The terpenoid benzoquinone, rhodoquinone (RQ), is essential to the bioenergetics of many organisms that survive in low oxygen environments. RQ biosynthesis and its regulation has potential as a novel target for anti-microbial and anti-parasitic drug development. Recent work has uncovered two distinct pathways for RQ biosynthesis which have evolved independently. The first pathway is used by bacteria, such as Rhodospirillum rubrum, and some protists that possess the rquA gene. These species derive their RQ directly from ubiquinone (UQ), the essential electron transporter used in the aerobic respiratory chain. The second pathway is used in animals, such as Caenorhabditis elegans and parasitic helminths, and requires 3-hydroxyanthranilic acid (3-HAA) as a precursor, which is derived from tryptophan through the kynurenine pathway. A COQ-2 isoform, which is unique to these species, facilitates prenylation of the 3-HAA precursor. After prenylation, the arylamine ring is further modified to form RQ using several enzymes common to the UQ biosynthetic pathway. In addition to current knowledge of RQ biosynthesis, we review the phylogenetic distribution of RQ and its function in anaerobic electron transport chains in bacteria and animals. Finally, we discuss key steps in RQ biosynthesis that offer potential as drug targets to treat microbial and parasitic infections, which are rising global health concerns.

Marbois B et al. (2005) J Biol Chem "Coq3 and Coq4 define a polypeptide complex in yeast mitochondria for the biosynthesis of coenzyme Q."

Poon WW, Clarke CF, Marbois B, Shepherd JN, Faull KF, Lee PT, Gin P, Strahan J

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J Biol Chem,

2005]

Coenzyme Q (Q) is a redox active lipid essential for aerobic respiration in eukaryotes. In Saccharomyces cerevisiae at least eight mitochondrial polypeptides, designated Coq1-Coq8, are required for Q biosynthesis. Here we present physical evidence for a coenzyme Q-biosynthetic polypeptide complex in isolated mitochondria. Separation of digitonin-solubilized mitochondrial extracts in one- and two-dimensional Blue Native PAGE analyses shows that Coq3 and Coq4 polypeptides co-migrate as high molecular mass complexes. Similarly, gel filtration chromatography shows that Coq1p, Coq3p, Coq4p, Coq5p, and Coq6p elute in fractions higher than expected for their respective subunit molecular masses. Coq3p, Coq4p, and Coq6p coelute with an apparent molecular mass exceeding 700 kDa. Coq3 O-methyltransferase activity, a surrogate for Q biosynthesis and complex activity, also elutes at this high molecular mass. We have determined the quinone content in lipid extracts of gel filtration fractions by liquid chromatography-tandem mass spectrometry and find that demethoxy-Q(6) is enriched in fractions with Coq3p. Co-precipitation of biotinylated-Coq3 and Coq4 polypeptide from digitonin-solubilized mitochondrial extracts shows their physical association. This study identifies Coq3p and Coq4p as defining members of a Q-biosynthetic Coq polypeptide complex.

Poon WW et al. (1999) J Biol Chem "Yeast and rat Coq3 and Escherichia coli UbiG polypeptides catalyze both O-methyltransferase steps in coenzyme Q biosynthesis."

Myles DC, Barkovich RJ, Clarke CF, Poon WW, Lee PT, Shepherd JN, Hsu AY, Frankel A

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J Biol Chem,

1999]

Ubiquinone (coenzyme Q or Q) is a lipid that functions in the electron transport chain in the inner mitochondrial membrane of eukaryotes and the plasma membrane of prokaryotes. Q-deficient mutants of Saccharomyces cerevisiae harbor defects in one of eight COQ genes (coq1-coq8) and are unable to grow on nonfermentable carbon sources. The biosynthesis of Q involves two separate O-methylation steps. In yeast, the first O-methylation utilizes 3, 4-dihydroxy-5-hexaprenylbenzoic acid as a substrate and is thought to be catalyzed by Coq3p, a 32.7-kDa protein that is 40% identical to the Escherichia coli O-methyltransferase, UbiG. In this study, farnesylated analogs corresponding to the second O-methylation step, demethyl-Q(3) and Q(3), have been chemically synthesized and used to study Q biosynthesis in yeast mitochondria in vitro. Both yeast and rat Coq3p recognize the demethyl-Q(3) precursor as a substrate. In addition, E. coli UbiGp was purified and found to catalyze both O-methylation steps. Futhermore, antibodies to yeast Coq3p were used to determine that the Coq3 polypeptide is peripherally associated with the matrix-side of the inner membrane of yeast mitochondria. The results indicate that one O-methyltransferase catalyzes both steps in Q biosynthesis in eukaryotes and prokaryotes and that Q biosynthesis is carried out within the matrix compartment of yeast mitochondria.

Tan JH et al. (2020) Elife "Alternative splicing of coq-2 controls the level of rhodoquinone in animals."

Shepherd JN, Reinl SR, Romanelli-Cedrez L, Schertzberg MR, Davis RE, Fraser AG, Lautens M, Salinas G, Tan JH, Wang J

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Elife,

2020]

Parasitic helminths use two benzoquinones as electron carriers in the electron transport chain. In normoxia they use ubiquinone (UQ), but in the anaerobic conditions inside the host, they require rhodoquinone (RQ) and greatly increase RQ levels. We previously showed the switch from UQ to RQ synthesis is driven by a change in substrates by the polyprenyltransferase COQ-2 (Del Borrello et al., 2019; Roberts Buceta et al., 2019) - how this substrate choice is made is unknown. Here, we show helminths make two coq-2 splice forms, coq-2a and coq-2e, and the coq-2e-specific exon is only found in species that make RQ. We show that in C. elegans COQ-2e is required for efficient RQ synthesis and for survival in cyanide. Crucially, parasites switch from COQ-2a to COQ-2e as they transition into anaerobic environments. We conclude helminths switch from UQ to RQ synthesis principally via changes in the alternative splicing of coq-2.

Buceta PMR et al. (2019) J Biol Chem "The kynurenine pathway is essential for rhodoquinone biosynthesis in Caenorhabditis elegans."

Schlatter TD, VonPaige ML, Culver JC, Drexelius JA, Higley TW, Babcock SJ, Carrera I, Buceta PMR, Shepherd JN, Xun H, Romanelli-Cedrez L, Salinas G, Davis DC

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J Biol Chem,

2019]

A key metabolic adaptation of some species that face hypoxia as part of their life-cycle involves an alternative electron transport chain in which rhodoquinone (RQ) is required for fumarate reduction and ATP production. RQ biosynthesis in bacteria and protists requires ubiquinone (Q) as a precursor. In contrast, Q is not a precursor for RQ biosynthesis in animals such as parasitic helminths, and most details of this pathway have remained elusive. Here, we used Caenorhabditis elegans as a model animal to elucidate key steps in RQ biosynthesis. Using RNAi and a series of C. elegans mutants, we found that arylamine metabolites from the kynurenine pathway are essential precursors for RQ biosynthesis de novo Deletion of kynu-1, encoding a kynureninase that converts L-kynurenine (KYN) to anthranilic acid (AA), and 3-hydroxykynurenine (3HKYN) to 3-hydroxyanthranilic acid (3HAA), completely abolished RQ biosynthesis, but did not affect Q levels. Deletion of kmo-1, which encodes a kynurenine 3-monooxygenase that converts KYN to HKYN, drastically reduced RQ, but not Q levels. Knockdown of the Q biosynthetic genes coq-5 and coq-6 affected both Q and RQ levels, indicating that both biosynthetic pathways share common enzymes. Our study reveals that two pathways for RQ biosynthesis have independently evolved. Unlike in bacteria, where amination is the last step in RQ biosynthesis, in worms, the pathway begins with the arylamine precursor AA or 3HAA. Since RQ is absent in mammalian hosts of helminths, inhibition of RQ biosynthesis may have potential utility for targeting parasitic infections that cause important neglected tropical diseases.

Zhang W et al. (2012) PLoS Genet "HAL-2 promotes homologous pairing during Caenorhabditis elegans meiosis by antagonizing inhibitory effects of synaptonemal complex precursors."

MacQueen AJ, Villeneuve AM, Miley N, Carlton PM, Sato A, Zhang W, Nabeshima K, Mlynarczyk-Evans S, Martinez-Perez E, Zastrow MS

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PLoS Genet,

2012]

During meiosis, chromosomes align with their homologous pairing partners and stabilize this alignment through assembly of the synaptonemal complex (SC). Since the SC assembles cooperatively yet is indifferent to homology, pairing and SC assembly must be tightly coordinated. We identify HAL-2 as a key mediator in this coordination, showing that HAL-2 promotes pairing largely by preventing detrimental effects of SC precursors (SYP proteins). hal-2 mutants fail to establish pairing and lack multiple markers of chromosome movement mediated by pairing centers (PCs), chromosome sites that link chromosomes to cytoplasmic microtubules through nuclear envelope-spanning complexes. Moreover, SYP proteins load inappropriately along individual unpaired chromosomes in hal-2 mutants, and markers of PC-dependent movement and function are restored in hal-2; syp double mutants. These and other data indicate that SYP proteins can impede pairing and that HAL-2 promotes pairing predominantly but not exclusively by counteracting this inhibition, thereby enabling activation and regulation of PC function. HAL-2 concentrates in the germ cell nucleoplasm and colocalizes with SYP proteins in nuclear aggregates when SC assembly is prevented. We propose that HAL-2 functions to shepherd SYP proteins prior to licensing of SC assembly, preventing untimely interactions between SC precursors and chromosomes and allowing sufficient accumulation of precursors for rapid cooperative assembly upon homology verification.