The
 bchU
 Gene of
 Chlorobium tepidum
 Encodes the C-20 Methyltransferase in Bacteriochlorophyll
 c
 Biosynthesis

Maresca, Julia A.; Chew, Aline Gómez Maqueo; Ponsatí, Marta Ros; Frigaard, Niels‐Ulrik; Ormerod, John G.; Bryant, Donald A.

doi:10.1128/jb.186.9.2558-2566.2004

Cited by 71 publications

(84 citation statements)

References 46 publications

(55 reference statements)

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“…vertical stratification of BChl-c-, BChl-d-and BChl-e containing organisms in lakes (see discussion in reference Maresca et al, 2004). Further niche partitioning undoubtedly explains the coexistence of different types of phototrophs using similar light wavelengths.…”

Section: Description Of Functional Guildsmentioning

confidence: 99%

Community ecology of hot spring cyanobacterial mats: predominant populations and their functional potential

et al. 2011

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Phototrophic microbial mat communities from 60 1C and 65 1C regions in the effluent channels of Mushroom and Octopus Springs (Yellowstone National Park, WY, USA) were investigated by shotgun metagenomic sequencing. Analyses of assembled metagenomic sequences resolved six dominant chlorophototrophic populations and permitted the discovery and characterization of undescribed but predominant community members and their physiological potential. Linkage of phylogenetic marker genes and functional genes showed novel chlorophototrophic bacteria belonging to uncharacterized lineages within the order Chlorobiales and within the Kingdom Chloroflexi. The latter is the first chlorophototrophic member of Kingdom Chloroflexi that lies outside the monophyletic group of chlorophototrophs of the Order Chloroflexales. Direct comparison of unassembled metagenomic sequences to genomes of representative isolates showed extensive genetic diversity, genomic rearrangements and novel physiological potential in native populations as compared with genomic references. Synechococcus spp. metagenomic sequences showed a high degree of synteny with the reference genomes of Synechococcus spp. strains A and B 0 , but synteny declined with decreasing sequence relatedness to these references. There was evidence of horizontal gene transfer among native populations, but the frequency of these events was inversely proportional to phylogenetic relatedness.

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Section: Description Of Functional Guildsmentioning

confidence: 99%

Community ecology of hot spring cyanobacterial mats: predominant populations and their functional potential

et al. 2011

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“…BS-1 (formerly Chlorobium phaeobacteroides BS-1) stably grows at the chemocline of the Black Sea, which occurs at a depth of ϳ100 -110 m beneath the surface (3,10,11). At this depth, the light intensity is nearly 10 6 -fold lower than at the surface, ϳ3 nmol of photons m Ϫ2 s Ϫ1 photons/day at the irradiance levels where these bacteria occur (12).…”

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“…BchQ and BchR methylate the resulting product at the C-8 2 and C-12 1 positions, respectively, to produce a family of related homologs (18). 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).…”

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“…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). Naturally occurring or genetically engineered mutants of bchU in formerly BChl c-producing strains exclusively synthesize BChl d (12,(32)(33)(34)(35).…”

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“…BChlide c was prepared from a 2-liter culture of the bciD mutant of C. limnaeum (see "Results"), and BChlide d was prepared from a 2-liter culture of the bchU mutant of C. tepidum (12). Cells were harvested by centrifugation, and pigments were extracted with 7:2 acetone/methanol (40 ml) for 1 h at room temperature in the dark with stirring.…”

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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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Chlorophylls

Fujita

2015

Encyclopedia of Life Sciences

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Chlorophylls (Chls) are a group of cyclic tetrapyrrole pigments that are involved in the light reactions of photosynthesis. There are many Chls differing in chemical structures; Chls a , b , c , d and f and bacteriochlorophylls (BChls) a , b , c , d , e , f and g . All Chls are classified into three groups by their parental structure; porphyrins, chlorins and bacteriochlorins. Upon absorption of light the Chl molecule transitions into the first excited singlet state, and the captured energy is transferred to the neighbouring Chl molecules reaching the reaction centre Chl molecules to ignite the photosynthetic electron transfer. All Chls are synthesised from 5‐aminolevulinic acid via multiple enzymatic reactions. The first half of this biosynthetic pathway is shared with haem biosynthesis and the second half is specific for Chls, which is the so‐called magnesium (Mg) branch. In the Mg branch, the reactions from protoporphyrin IX to chlorophyllide a constitute a common pathway for all Chls. Key Concepts Chlorophylls have a central role in light harvesting and ignition of photosynthetic electron transfer. Chlorophylls are functionally divided into antenna chlorophylls and reaction centre chlorophylls. A variety of chemically different chlorophylls absorb different wavelengths of light, and photosynthetic organisms have specific sets of chlorophylls for utilising light in their natural habitats. All chlorophylls are synthesised from 5‐aminolaevulinic acid, and the subsequent six reactions leading to protoporphyrin IX are common to haem biosynthesis. Five reactions from protoporphyrin IX to chlorophyllide a are shared with the biosynthetic pathways of all chlorophylls. The diversity of the biosynthetic pathways of different chlorophylls results from the evolution of photosynthetic organisms to adapt their light environments. Chlorophyll biosynthesis is tightly regulated by multiple layers of regulatory mechanisms to avoid photooxidative damage caused by biosynthetic intermediates. Elucidation of the reaction mechanisms of enzymes involved in the magnesium branch is one of the most important goals in plant physiology.

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The bchU Gene of Chlorobium tepidum Encodes the C-20 Methyltransferase in Bacteriochlorophyll c Biosynthesis

Cited by 71 publications

References 46 publications

Community ecology of hot spring cyanobacterial mats: predominant populations and their functional potential

Community ecology of hot spring cyanobacterial mats: predominant populations and their functional potential

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

Chlorophylls

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