Chlorobium tepidum
 Mutant Lacking Bacteriochlorophyll
 c
 Made by Inactivation of the
 bchK
 Gene, Encoding Bacteriochlorophyll
 c
 Synthase

Frigaard, Niels‐Ulrik; Voigt, Ginny D.; Bryant, Donald A.

doi:10.1128/jb.184.12.3368-3376.2002

Cited by 70 publications

(82 citation statements)

References 45 publications

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“…The solvent system for analysis of all strains was modified from the previously described system (73). Solvent B was 50% methanol, 30% ethyl acetate, and 20% acetonitrile, and solvent A consisted of water:methanol:acetonitrile (62.5:21:16.5) containing 10 mM ammonium acetate.…”

Section: Inactivation Of Ct0456mentioning

confidence: 99%

Identification of a fourth family of lycopene cyclases in photosynthetic bacteria

Maresca

Graham

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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A fourth and large family of lycopene cyclases was identified in photosynthetic prokaryotes. The first member of this family, encoded by the cruA gene of the green sulfur bacterium Chlorobium tepidum, was identified in a complementation assay with a lycopene-producing strain of Escherichia coli. Orthologs of cruA are found in all available green sulfur bacterial genomes and in all cyanobacterial genomes that lack genes encoding CrtL-or CrtY-type lycopene cyclases. The cyanobacterium Synechococcus sp. PCC 7002 has two homologs of CruA, denoted CruA and CruP, and both were shown to have lycopene cyclase activity. Although all characterized lycopene cyclases in plants are CrtL-type proteins, genes orthologous to cruP also occur in plant genomes. The CruA-and CruP-type carotenoid cyclases are members of the FixC dehydrogenase superfamily and are distantly related to CrtL-and CrtY-type lycopene cyclases. Identification of these cyclases fills a major gap in the carotenoid biosynthetic pathways of green sulfur bacteria and cyanobacteria.carotenogenesis ͉ carotenoids ͉ cyanobacteria ͉ green sulfur bacteria ͉ photosynthesis C olored carotenoids are found in nearly all photosynthetic species and in a variety of nonphotosynthetic organisms and play roles in light-harvesting, photoprotection, structural maintenance of pigment-protein complexes (1), and membrane structure and fluidity (2). The cyclization of the linear compound lycopene to produce ␣-, ␤-, ␥-, or -carotene is a branch point in carotenoid biosynthetic pathways in many species of bacteria, plants, and fungi (3, 4). The monocyclic ␥-carotene is a precursor to myxoxanthophylls in cyanobacteria (5, 6), is both an intermediate and an end product of carotenogenesis in orange and yellow flowers and fruits (7-10), and is an intermediate in chlorobactene biosynthesis in green sulfur bacteria (GSB) (11-13). Dicyclic ␤-carotene is a major component of photosystems (PS) I and II in cyanobacteria and plants (14,15) and is modified to isorenieratene in brown-colored GSB and some actinomycetes (16,17).Three classes of lycopene cyclases have previously been identified in bacteria: the CrtY-type ␤-cyclases that are found in many carotenogenic proteobacteria (e.g., refs. 18 and 19), Streptomyces spp. (17), and the Chloroflexi; the CrtL family, which includes the ␤-and -cyclases in some cyanobacteria and plants (20,21); and the heterodimeric cyclases of some Gram-positive bacteria (22, 23), which are related to the lycopene cyclases of archaea (24, 25) and halophilic bacteria (26). These classes are distantly related to each other and share only a few conserved motifs, including an N-terminal flavin-binding domain that is found in the first two groups but appears to be missing in the third (27). Carotenoid monocyclases are found in both the CrtY and CrtL families (28-30), and there are no obvious sequence differences between mono-and dicyclases (28).The cyclization of lycopene to ␥-or ␤-carotene is an isomerization reaction, which produces no net change in mass or redox state o...

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Section: Inactivation Of Ct0456mentioning

confidence: 99%

Identification of a fourth family of lycopene cyclases in photosynthetic bacteria

Maresca

Graham

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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133

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“…3 In contrast, the bchJ::aadA cells were orange in color, which suggested that these cells had a severely reduced BChl c content (see Refs. 19). The whole cell absorption spectrum of the mutant and wild-type cells confirmed this observation (Fig.…”

Section: Hplc and Hplc-ms Of Chls In The Ct1063mentioning

confidence: 99%

“…2, A and B). The resulting plasmids were linearized by digestion with AhdI and used to transform wild-type C. tepidum cells as described (19). Segregation of the mutants was confirmed by PCR as described (19) (see Fig.…”

Section: Methodsmentioning

confidence: 99%

Characterization of a Plant-like Protochlorophyllide a Divinyl Reductase in Green Sulfur Bacteria

Chew

Bryant

2007

Journal of Biological Chemistry

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The green sulfur bacterium Chlorobium tepidum synthesizes three types of (bacterio)chlorophyll ((B)Chl): BChl a P , Chl a PD , and BChl c F . During the synthesis of all three molecules, a C-8 vinyl substituent is reduced to an ethyl group, and in the case of BChl c F , the C-8 2 carbon of this ethyl group is subsequently methylated once or twice by the radical S-adenosylmethionine enzyme BchQ. The C. tepidum genome contains homologs of two genes, bchJ (CT2014) and CT1063, that are highly homologous to genes, bchJ and AT5G18660, and that have been reported to encode C-8 vinyl reductases in Rhodobacter capsulatus and Arabidopsis thaliana, respectively. To determine which gene product actually encodes a C-8 vinyl reductase activity, the bchJ and CT1063 genes were insertionally inactivated in C. tepidum.

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“…Specifically, the enzymes responsible for adding the esterifying alcohols to Chls and BChls show considerable specificity for the (B)Chlide substrate but usually have broader specificity for the esterifying alcohol (20,(51)(52)(53). In C. tepidum BchK is responsible for the addition of the farnesyl tail to BChl c, and ChlG and BchG add phytadienol and phytol to Chl a and BChl a, respectively (20). A comparative analysis of the genomes of GSB shows that all have at least three esterifying enzymes: BchK, ChlG, and BchG.…”

Section: Discussionmentioning

confidence: 99%

“…These methylation homologs are then hydroxylated at C-3 1 by BchF or BchV to produce bacteriochlorophyllide (BChlide) d (21,(27)(28)(29), and in BChl c-producing strains, they are subsequently methylated by BchU at C-20 to produce BChlide c homologs (12,30,31). Finally, the BChlide c or BChlide d homologs are esterified with farnesol pyrophosphate by BchK to produce BChl c or BChl d homologs with differing numbers of methyl groups (20). The methylation reactions catalyzed by BchU, BchQ, and BchR help to tune the absorption properties of BChl c, d, and e in chlorosomes and also lead to inhomogeneous broadening of the nearinfrared absorption band of aggregated BChls in chlorosomes (12,17,18).…”

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confidence: 99%

BciD Is a Radical S-Adenosyl-l-methionine (SAM) Enzyme That Completes Bacteriochlorophyllide e Biosynthesis by Oxidizing a Methyl Group into a Formyl Group at C-7

Thweatt

Ferlez

Golbeck

et al. 2017

Journal of Biological Chemistry

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Edited by Joseph JezGreen bacteria are chlorophotorophs that synthesize bacteriochlorophyll (BChl) c, d, or e, which assemble into supramolecular, nanotubular structures in large light-harvesting structures called chlorosomes. The biosynthetic pathways of these chlorophylls are known except for one reaction. Null mutants of bciD, which encodes a putative radical S-adenosyl-L-methionine (SAM) protein, are unable to synthesize BChl e but accumulate BChl c; however, it is unknown whether BciD is sufficient to convert BChl c (or its precursor, bacteriochlorophyllide (BChlide) c) into BChl e (or BChlide e). To determine the function of BciD, we expressed the bciD gene of Chlorobaculum limnaeum strain DSMZ 1677 T in Escherichia coli and purified the enzyme under anoxic conditions. Electron paramagnetic resonance spectroscopy of BciD indicated that it contains a single [4Fe-4S] cluster. In assays containing SAM, BChlide c or d, and sodium dithionite, BciD catalyzed the conversion of SAM into 5-deoxyadenosine and BChlide c or d into BChlide e or f, respectively. Our analyses also identified intermediates that are proposed to be 7 1 -OH-BChlide c and d. Thus, BciD is a radical SAM enzyme that converts the methyl group of BChlide c or d into the formyl group of BChlide e or f. This probably occurs by a mechanism involving consecutive hydroxylation reactions of the C-7 methyl group to form a geminal diol intermediate, which spontaneously dehydrates to produce the final products, BChlide e or BChlide f. The demonstration that BciD is sufficient to catalyze the conversion of BChlide c into BChlide e completes the biosynthetic pathways for all "Chlorobium chlorophylls."

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Chlorobium tepidum Mutant Lacking Bacteriochlorophyll c Made by Inactivation of the bchK Gene, Encoding Bacteriochlorophyll c Synthase

Cited by 70 publications

References 45 publications

Identification of a fourth family of lycopene cyclases in photosynthetic bacteria

Identification of a fourth family of lycopene cyclases in photosynthetic bacteria

Characterization of a Plant-like Protochlorophyllide a Divinyl Reductase in Green Sulfur Bacteria

BciD Is a Radical S-Adenosyl-l-methionine (SAM) Enzyme That Completes Bacteriochlorophyllide e Biosynthesis by Oxidizing a Methyl Group into a Formyl Group at C-7

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