Bacteriochlorophyll Biosynthesis Research Articles

Some factors controlling the biosynthesis of chlorosome antenna bacteriochlorophylls in green filamentous anoxygenic phototrophic bacteria of the family Oscillochloridaceae

We determined the concentrations of bacteriochlorophylls (BChl) in the light-harvesting antennae of Oscillochloris trichoides (of the family Oscillochloridaceae belonging to green filamentous mesophilic bacteria) cultivated either with gabaculine, an inhibitor of the C-5 pathway of BChl biosynthesis in a number of bacteria, or at various illumination intensities. We determined the BChl c: BChl a molar ratios in intact cells, in chlorosome-membrane complexes, and in isolated chlorosomes. We revealed that BChl c synthesis in Osc. trichoides was more gabaculine-sensitive than BChl a synthesis. Accordingly, an increase in gabaculine concentrations in the medium resulted in a decrease in the BChl c: BChl a ratio in the tested samples. We suggest that BChl synthesis in Osc. trichoides proceeds via the C-5 pathway, similar to representatives of other families of green bacteria (Chlorobium limicola and Chloroflexus aurantiacus). We demonstrated that the BChl c: BChl a ratio in the chlorosomes varied from 55 : 1 to 110 : 1, depending on light intensity. This ratio is, therefore, closer to that of Chlorobiaceae, and it significantly exceeds the BChl c: BChl a ratio in Chloroflexaceae.

緑色硫黄細菌Chlorobium tepidum由来のメチル基転移酵素BchUのバクテリオクロロフィル c合成経路における役割

緑色硫黄細菌Chlorobium tepidum由来のメチル基転移酵素BchUのバクテリオクロロフィル c合成経路における役割

Evolution of photosynthesis and biospheric oxygenation contingent upon nitrogen fixation?

How photosynthesis by Precambrian cyanobacteria oxygenated Earth's biosphere remains incompletely understood. Here it is argued that the oxic transition, which took place between approximately 2.3 and 0.5 Gyr ago, required a great proliferation of cyanobacteria, and this in turn depended on their ability to fix nitrogen via the nitrogenase enzyme system. However, the ability to fix nitrogen was not a panacea, and the rate of biospheric oxygenation may still have been affected by nitrogen constraints on cyanobacterial expansion. Evidence is presented for why cyanobacteria probably have a greater need for fixed nitrogen than other prokaryotes, underscoring the importance of their ability to fix nitrogen. The connection between nitrogen fixation and the evolution of photosynthesis is demonstrated by the similarities between nitrogenase and enzymes critical for the biosynthesis of (bacterio)chlorophyll. It is hypothesized that biospheric oxygenation would not have occurred if the emergence of cyanobacteria had not been preceded by the evolution of nitrogen fixation, and if these organisms had not also acquired the ability to fix nitrogen at the beginning of or very early in their history. The evolution of nitrogen fixation also appears to have been a precondition for the evolution of (bacterio)chlorophyll-based photosynthesis. Given that some form of chlorophyll is obligatory for true photosynthesis, and its light absorption and chemical properties make it a ‘universal pigment’, it may be predicted that the evolution of nitrogen fixation and photosynthesis are also closely linked on other Earth-like planets.

Crystal Structure of a RuBisCO-like Protein from the Green Sulfur Bacterium Chlorobium tepidum

Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) catalyzes the incorporation of atmospheric CO(2) into ribulose 1,5-bisphosphate (RuBP). RuBisCOs are classified into four forms based on sequence similarity: forms I, II and III are bona fide RuBisCOs; form IV, also called the RuBisCO-like protein (RLP), lacks several of the substrate binding and catalytic residues and does not catalyze RuBP-dependent CO(2) fixation in vitro. To contribute to understanding the function of RLPs, we determined the crystal structure of the RLP from Chlorobium tepidum. The overall structure of the RLP is similar to the structures of the three other forms of RuBisCO; however, the active site is distinct from those of bona fide RuBisCOs and suggests that the RLP is possibly capable of catalyzing enolization but not carboxylation. Bioinformatic analysis of the protein functional linkages suggests that this RLP coevolved with enzymes of the bacteriochlorophyll biosynthesis pathway and may be involved in processes related to photosynthesis.

Clustering of Genes with Function in the Biosynthesis of Bacteriochlorophyll and Heme in the Green Sulfur Bacterium Chlorobium Vibrioforme

identical to the pathway of heme biosynthesis (Fig. 1). The formation of 5- aminolevulinate can be achieved either from glycine and succinyl-CoA, in a reaction catalyzed by the enzyme 5-aminolevulinic acid synthase, or by a three step pathway from glutamate catalyzed by three enzymes, of which the second is glutamyl- tRNA dehydrogenase ( BEALE 1995). The succinyl- CoA pathway is used by nonplant eukaryotes and a group of bacteria that includes the purple photo- synthetic bacteria

Biosynthesis of Chlorophylls from Protoporphyrin IX

AbstractFor Abstract see ChemInform Abstract in Full Text.

Molecular Mechanisms of Photosynthesis. By Robert E Blankenship. Oxford and Malden (Massachusetts): Blackwell Science. $49.95 (paper). ix + 321 p + 6 pl; ill.; index. ISBN: 0–632–04321–0. 2002.

Previous articleNext article No AccessPlant SciencesMolecular Mechanisms of Photosynthesis. By Robert E Blankenship. Oxford and Malden (Massachusetts): Blackwell Science. $49.95 (paper). ix + 321 p + 6 pl; ill.; index. ISBN: 0–632–04321–0. 2002.T Cavalier‐SmithT Cavalier‐SmithZoology, University of Oxford, Oxford, United Kingdom Search for more articles by this author Zoology, University of Oxford, Oxford, United KingdomPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 78, Number 2June 2003 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/377978 Views: 97Total views on this site Citations: 1Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Jürgen Moser, Gunhild Layer Enzymatic Systems with Homology to Nitrogenase: Biosynthesis of Bacteriochlorophyll and Coenzyme F430, (Oct 2018): 25–35.https://doi.org/10.1007/978-1-4939-8864-8_2

Biosynthesis of chlorophylls from protoporphyrin IX.

A review of the biosynthesis of chlorophylls and bacteriochlorophylls from protoporphyrin IX with 235 references. The literature on the enzymes magnesium chelatase, S-adenosyl-L-methionine:magnesium protoporphyrin IX O-methyltransferase, magnesium-protoporphyrin IX monomethyl ester oxidative cyclase, protochlorophyllide oxidoreductase, chlorophyll synthase, bacteriochlorophyll synthase, protochlorophyllide 8-vinyl reductase and chlorophyll a oxidase from 1989 is discussed.

Horizontal transfer of the photosynthesis gene cluster and operon rearrangement in purple bacteria.

A 37-kb photosynthesis gene cluster was sequenced in a photosynthetic bacterium belonging to the beta subclass of purple bacteria (Proteobacteria), Rubrivivax gelatinosus. The cluster contained 12 bacteriochlorophyll biosynthesis genes (bch), 7 carotenoid biosynthesis genes (crt), structural genes for photosynthetic apparatuses (puf and puh), and some other related genes. The gene arrangement was markedly different from those of other purple photosynthetic bacteria, while two superoperonal structures, crtEF-bchCXYZ-puf and bchFNBHLM-lhaA-puhA, were conserved. Molecular phylogenetic analyses of these photosynthesis genes showed that the photosynthesis gene cluster of Rvi. gelatinosus was originated from those of the species belonging to the alpha subclass of purple bacteria. It was concluded that a horizontal transfer of the photosynthesis gene cluster from an ancestral species belonging to the alpha subclass to that of the beta subclass of purple bacteria had occurred and was followed by rearrangements of the operons in this cluster.

Photosynthesis gene regulation in Rubrivivax gelatinosus; transcription factor PpsR is involved in both negative and positive control

Induction of the photosystem biosynthesis in anoxygenic photosynthetic bacteria arises in the absence of oxygen. The regulation of this induction occurs at the transcriptional level, with photosynthesis genes expressed preferentially under anaerobic conditions. Here we report analysis of the transcriptional control of three photosynthesis promoters, puc (light-harvesting II apoproteins), crtI (carotenoid biosynthesis) and bchG (bacteriochlorophyll biosynthesis) by the ppsR transcription factor in R. gelatinosus. This was accomplished by analysing the photosytem production in the wild type and in the PpsR null mutant grown under anaerobic and semiaerobic conditions and by assessing the beta galactosidase activity of lacZ transcriptionnal fusion to promoters possessing the putative ppsR binding boxes. It was found that under semi-aerobic conditions, while inactivation of the ppsR gene results in overproduction of carotenoid pigments, the production bacteriochlorophyll was slightely reduced and the production of LHII was completely abolished. These finding suggest that in contrast to what has been found previously for Rhodobacter species, PpsR acts in R. gelatinosus as an aerobe repressor of crtI gene, meanwhile it acts as an aerobe activator for the expression of both pucBA and an unyet identified bch gene. These results were confirmed by the b-galactosidase activities from pucB::lacZ and crtl::lacZ fusions. Inspection of the putative ppsR binding boxes revealed significant differences (sequence and spacing between the boxes) that could explain the different levels of expression of the studied genes and based on these analyses a model addressing the PpsR involvement in positive and negative regulation is proposed.

Investigation of bacteriochlorophyll biosynthesis genes in Blastochloris viridis by functional complementation of mutants of Rhodobacter capsulatus

Blastochloris (formerly Rhodopseudomonas) viridis produces bacteriochlorophyll (BChl) b which is distinguished from BChl a by the possession of an ethylidene group at C8 instead of an ethyl. This chemical structure enables to BChl b to absorb longer wave length light (~1100 nm) than BChl a. To investigate genes involved in the BChl b biosynthesis, we have constructed genomic DNA libraries from B. viridis and introduced them to mutants of the nonsulfur purple bacterium Rhodobacter capsulatus which is deficient in BChl a biosynthesis. Total ten kinds of R. capsulatus mutants, three Mg-chelatase (BchD, H, I) mutants, three protochlorophyllide reductase (BchB, L, N) mutants, Mg-protoporphyrin IX methyltransferase (BchM) mutant, Mg-protoporphyrin IX monomethylester oxidative cyclase (BchE) mutant, bacteriochlorophyll synthase (Bch G) mutant, and 2-vinyl-bacteriochlorophyllide hydratase (BchF) mutant, were functionally complemented by B. viridis library DNA. The complemented R. capsulatus strains were demonstrated to be capable of synthesizing BChl a under photoautotrophic growth conditions.

Molecular evidence for the early evolution of photosynthesis.

The origin and evolution of photosynthesis have long remained enigmatic due to a lack of sequence information of photosynthesis genes across the entire photosynthetic domain. To probe early evolutionary history of photosynthesis, we obtained new sequence information of a number of photosynthesis genes from the green sulfur bacterium Chlorobium tepidum and the green nonsulfur bacterium Chloroflexus aurantiacus. A total of 31 open reading frames that encode enzymes involved in bacteriochlorophyll/porphyrin biosynthesis, carotenoid biosynthesis, and photosynthetic electron transfer were identified in about 100 kilobase pairs of genomic sequence. Phylogenetic analyses of multiple magnesium-tetrapyrrole biosynthesis genes using a combination of distance, maximum parsimony, and maximum likelihood methods indicate that heliobacteria are closest to the last common ancestor of all oxygenic photosynthetic lineages and that green sulfur bacteria and green nonsulfur bacteria are each other's closest relatives. Parsimony and distance analyses further identify purple bacteria as the earliest emerging photosynthetic lineage. These results challenge previous conclusions based on 16S ribosomal RNA and Hsp60/Hsp70 analyses that green nonsulfur bacteria or heliobacteria are the earliest phototrophs. The overall consensus of our phylogenetic analysis, that bacteriochlorophyll biosynthesis evolved before chlorophyll biosynthesis, also argues against the long-held Granick hypothesis.

Reconstitution of Light-independent Protochlorophyllide Reductase from Purified Bchl and BchN-BchB Subunits: IN VITRO CONFIRMATION OF NITROGENASE-LIKE FEATURES OF A BACTERIOCHLOROPHYLL BIOSYNTHESIS ENZYME

Protochlorophyllide reductase catalyzes the reductive formation of chlorophyllide from protochlorophyllide during biosynthesis of chlorophylls and bacteriochlorophylls. The light-independent (dark) form of protochlorophyllide reductase plays a key role in the ability of gymnosperms, algae, and photosynthetic bacteria to green (form chlorophyll) in the dark. Genetic and sequence analyses have indicated that dark protochlorophyllide reductase consists of three protein subunits that exhibit significant sequence similarity to the three subunits of nitrogenase, which catalyzes the reductive formation of ammonia from dinitrogen. However, unlike the well characterized features of nitrogenase, there has been no previous biochemical characterization of dark protochlorophyllide reductase. In this study, we report the first reproducible demonstration of dark protochlorophyllide reductase activity from purified protein subunits that were isolated from the purple nonsulfur photosynthetic bacterium Rhodobacter capsulatus. Two of the three subunits (Bchl and BchN) were expressed in R. capsulatus as S tag fusion proteins that facilitated affinity purification. The third subunit (BchB) was co-purified with the BchN protein indicating that BchN and BchB proteins form a tight complex. Dark protochlorophyllide reductase activity was shown to be dependent on the presence of all three subunits, ATP, and the reductant dithionite. The similarity of dark protochlorophyllide reductase to nitrogenase is discussed.

Role of the H protein in assembly of the photochemical reaction center and intracytoplasmic membrane in Rhodospirillum rubrum.

Rhodospirillum rubrum is a model for the study of membrane formation. Under conditions of oxygen limitation, this facultatively phototrophic bacterium forms an intracytoplasmic membrane that houses the photochemical apparatus. This apparatus consists of two pigment-protein complexes, the light-harvesting antenna (LH) and photochemical reaction center (RC). The proteins of the photochemical components are encoded by the puf operon (LHalpha, LHbeta, RC-L, and RC-M) and by puhA (RC-H). R. rubrum puf interposon mutants do not form intracytoplasmic membranes and are phototrophically incompetent. The puh region was cloned, and DNA sequence determination identified open reading frames bchL and bchM and part of bchH; bchHLM encode enzymes of bacteriochlorophyll biosynthesis. A puhA/G115 interposon mutant was constructed and found to be incapable of phototrophic growth and impaired in intracytoplasmic membrane formation. Comparison of properties of the wild-type and the mutated and complemented strains suggests a model for membrane protein assembly. This model proposes that RC-H is required as a foundation protein for assembly of the RC and highly developed intracytoplasmic membrane. In complemented strains, expression of puh occurred under semiaerobic conditions, thus providing the basis for the development of an expression vector. The puhA gene alone was sufficient to restore phototrophic growth provided that recombination occurred.

Magnesium Insertion by Magnesium Chelatase in the Biosynthesis of Zinc Bacteriochlorophyll a in an Aerobic Acidophilic Bacterium Acidiphilium rubrum

To elucidate the mechanism for formation of zinc-containing bacteriochlorophyll a in the photosynthetic bacterium Acidiphilium rubrum, we isolated homologs of magnesium chelatase subunits (bchI, -D, and -H). A. rubrum bchI and -H were encoded by single genes located on the clusters bchP-orf168-bchI-bchD-orf320-crtI and bchF-N-B-H-L as in Rhodobacter capsulatus, respectively. The deduced sequences of A. rubrum bchI, -D, and -H had overall identities of 59. 8, 40.5, and 50.7% to those from Rba. capsulatus, respectively. When these genes were introduced into bchI, bchD, and bchH mutants of Rba. capsulatus for functional complementation, all mutants were complemented with concomitant synthesis of bacteriochlorophyll a. Analyses of bacteriochlorophyll intermediates showed that A. rubrum cells accumulate magnesium protoporphyrin IX monomethyl ester without detectable accumulation of zinc protoporphyrin IX or its monomethyl ester. These results indicate that a single set of magnesium chelatase homologs in A. rubrum catalyzes the insertion of only Mg(2+) into protoporphyrin IX to yield magnesium protoporphyrin IX monomethyl ester. Consequently, it is most likely that zinc-containing bacteriochlorophyll a is formed by a substitution of Zn(2+) for Mg(2+) at a step in the bacteriochlorophyll biosynthesis after formation of magnesium protoporphyrin IX monomethyl ester.

In vitro activation and repression of photosynthesis gene transcription in Rhodobacter capsulatus.

It has been known for over half a century that anoxygenic photosynthetic bacteria maximally synthesize their photosystems in the absence of oxygen. During the last decade, it has become clear that this regulation is largely at the transcriptional level, with photosynthesis genes expressed only under anaerobic conditions. We describe here in vitro reconstitution of activation and repression of three photosynthesis promoters, bch (bacteriochlorophyll biosynthesis), puc (light-harvesting II apoproteins) and puf (reaction centre and light-harvesting I apoproteins) using purified transcription factors and RNA polymerase from Rhodobacter capsulatus. Previous genetic results have indicated that each of these three promoters is differentially regulated by three key regulators: CrtJ acting as a repressor of bch and puc and the two-component regulators RegA/RegB, which are activators of puc and puf. These regulators are distinct from those that mediate oxygen control in enteric bacteria. Our in vitro studies show that these purified regulators directly control the expression of the housekeeping RNA polymerase at these promoters. High-level basal expression of the bch promoter is shown to be repressed by CrtJ. The puc promoter is activated by the RegB-phosphorylated RegA protein and additionally repressed by CrtJ. At the puc promoter, CrtJ effectively competes for promoter binding with RegA, while at the bch promoter, repression appears to be by competition for the RNA polymerase binding site. In contrast to what has been suggested previously, the RegA-activated puf promoter is demonstrated as being recognized by the housekeeping RNA polymerase. We also discuss evidence that RegA approximately P activation of the puc and puf promoters involves recruitment of RNA polymerase by different modes of protein-protein interaction.

Crystallization and preliminary X-ray analysis of the Rhodobacter capsulatus magnesium chelatase BchI subunit.

The Rhodobacter capsulatus BchI protein is one of three subunits of Mg chelatase, the enzyme which catalyzes the first committed step of chlorophyll and bacteriochlorophyll biosynthesis. The BchI protein was produced with an inducible T7 RNA polymerase expression system in Escherichia coli. The protein was purified from the soluble cell-extract fraction and crystallized from polyethylene glycol solution. The crystals diffract to a minimum Bragg spacing of 2.1 A. The space group is P63 with unit-cell dimensions a = b = 90.6, c = 84.1 A.

Coregulation of the syntheses of bacteriochlorophyll and pigment-binding proteins in Rhodobacter capsulatus

We quantified the expression of the puf and puc operons, which encode pigment binding proteins, in a number of strains of Rhodobacter capsulatus that have defects in genes affecting different steps of bacteriochlorophyll biosynthesis. Our results show that these mutations have a very similar effect on puf and puc expression. This suggests that the reduced expression of genes encoding pigment-binding proteins is due neither to the accumulation of a specific intermediate of bacteriochlorophyll synthesis nor to the lack of an early intermediate, but is rather the result of the lack of a very late intermediate or the bacteriochlorophyll molecule itself.

Molecular basis for semidominance of missense mutations in the XANTHA-H (42-kDa) subunit of magnesium chelatase.

During biosynthesis of bacteriochlorophyll or chlorophyll, three protein subunits of 140, 70, and 42 kDa interact to insert Mg2+ into protoporphyrin IX. The semidominant Chlorina-125, -157, and -161 mutants in barley are deficient in this step and accumulate protoporphyrin IX after feeding on 5-aminolevulinate. Chlorina-125, -157, and -161 are allelic to the recessive xantha-h mutants and contain G559A, G806A, and C271T mutations, respectively. These mutations cause single amino acid substitutions in residues that are conserved in all known primary structures of the 42-kDa subunit. In vitro complementation and reconstitution of Mg-chelatase activity show that the 42-kDa subunits are defective in the semidominant Chlorina mutants. A mutated protein is maintained in the Chlorina plastids, unlike in the xantha-h plastids. Heterozygous Chlorina seedlings have 25-50% of the Mg-chelatase activity of wild-type seedlings. Codominant expression of active and inactive 42-kDa subunits in heterozygous Chlorina seedlings is likely to produce two types of heterodimers between the strongly interacting 42-kDa and 70-kDa subunits. Reduced Mg-chelatase activity is explained by the capacity of heterodimers consisting of mutated 42-kDa and wild-type 70-kDa protein to bind to the 140-kDa subunit. The 42-kDa subunit is similar to chaperones that refold denatured polypeptides with respect to its ATP-to-ADP exchange activity and its ability to generate ATPase activity with the 70-kDa subunit. We hypothesize that the association of the 42-kDa subunit with the 70-kDa subunit allows them to form a specific complex with the 140-kDa subunit and that this complex inserts Mg2+ into protoporphyrin IX.

Genes encoding light-harvesting and reaction center proteins from Chromatium vinosum

Sequencing of a 3.4 kb DNA fragment isolated from the photosynthetic purple sulfur bacterium Chromatium vinosum and of PCR products has resulted in identification of the Chr. vinosum pufL, pufM, and pufC genes, reading from the 5′ to the 3′ direction, and coding, respectively, for the L, M and cytochrome c subunits of the reaction center of this bacterium. Other PCR products have been used to obtain complete sequences for the pufB and pufA genes, located immediately upstream from pufL and encoding the apoproteins of two Chr. vinosum light- harvesting proteins. The 3′-portion of the bchZ gene, a gene that codes for a protein involved in the biosynthesis of bacteriochlorophyll, has been located immediately upstream from pufB. A second pufB gene, pufB2, has been located downstream from pufC, as has the 5′-portion of a second pufA gene, pufA2. The location of a second set of pufB and pufA genes, encoding light- harvesting proteins, downstream from pufC has not previously been reported for any photosynthetic bacterium. Translation of the gene sequences encoding these Chr. vinosum light-harvesting proteins reveals both similarities to and differences from the amino acid sequences, obtained from direct sequencing of the apoproteins, previously reported for Chr. vinosum light-harvesting proteins. Translation of these gene sequences, and of those for pufL, pufM and pufC, revealed significant homology, at the amino acid level, to the corresponding peptides of photosynthetic purple non-sulfur bacteria.