Regulation of tetrapyrrole synthesis by light in chemostat cultures of Rhodobacter sphaeroides

Oelze, J.

doi:10.1128/jb.170.10.4652-4657.1988

Cited by 12 publications

(8 citation statements)

References 31 publications

(29 reference statements)

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“…Furthermore, chlorophyll a and chlorophyll b increase the stability of the nuclear-encoded LHCI and LHCII chlorophyll a/b apoproteins (31,32). Likewise, bacteriochlorophyll-binding proteins of photosynthetic bacteria turn over rapidly when bacteriochlorophyll levels are limiting (33)(34)(35). In higher plant chloroplasts, the regulatory mechanism described here affects the accumulation of a large number of abundant chloroplast proteins, giving it special significance during chloroplast biogenesis.…”

Section: Resultsmentioning

confidence: 90%

Chlorophyll regulates accumulation of the plastid-encoded chlorophyll apoproteins CP43 and D1 by increasing apoprotein stability.

Mullet

Klein

1990

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

209

106

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Chlorophyll apoprotein accumulation in higher plant chloroplasts is controlled by light-dependent chlorophyll' formation. Dark-grown plants lack chlorophyll and chlorophyl apoproteins. However, the plastid genes' encoding the chlorophyll apoproteins are transcribed; chlorophyll apoprotein mRNA accumulates and associates with polysomes in plastids of dark-grown plants. Pulse-labeling assays revealed a population of short-lived proteins in plastids of dark-grown plants. One of these transiently labeled proteins was CP43, a chlorophyll apoprotein associated with photosystem II. Plse chase assays showed that newly synthesized CP43 was rapidly degraded in plastids of dark-grown plants, which lack chlorophyll. In contrast, CP43 synthesized in plastids from illuminated plants was stable. The synthesis of D1, a chlorophyll apoprotein of the photosystem II reaction center, was also analyzed in plastids of dark-grown and illuminated plants. Radiolabel accumulation into full-length D1 was only 'detected in plastids of illuminated plants. However, Dl translation intermediates of 15-25 kDa were detected in both plastid populations. Pulse-chase assays showed that the 15-to 25-kDa D1 translation products were precursors of mature D1 in plastids of illuminated plants. In contrast, in plastids of darkgrown plants, the 15-to 25-kDa translation intermediates were converted into a 23-kDa polypeptide previously suggested to be a proteolytic product of Dl. These results indicate that chlorophyll produced in illuminated plants stabilizes D1 nascent polypeptides, which allows accumulation of mature DM.Chlorophyll is the key chromophore involved in plant photosynthetic light reactions. This chromophore mediates lightdependent charge separation in photosystem I (PSI) and photosystem II (PSII) and serves as the primary lightharvesting pigment in these photosystems. Chlorophyll is noncovalently associated with at least 12 different membrane-bound proteins of the thylakoid. PSII reaction centers contain two plastid-encoded chlorophyll-binding proteins, D1 although radiolabeling studies failed to detect amino acid incorporation into D1, CP43, CP47, and the P700 chlorophyll apoproteins (10). Within 5 min after dark-grown plants are illuminated, amino acid incorporation into D1, CP43, CP47, and the P700 chlorophyll apoproteins can be detected, and the chlorophyll apoproteins begin to accumulate (11,14,20). The light-dependent activation 'of chlorophyll apoprotein accumulation is controlled by protochlorophyllide reductase and requires formation of chlorophyll a (11,20 4038The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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Section: Resultsmentioning

confidence: 90%

Chlorophyll regulates accumulation of the plastid-encoded chlorophyll apoproteins CP43 and D1 by increasing apoprotein stability.

Mullet

Klein

1990

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

209

106

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“…Most of the attention has been devoted to regulation by oxygen tension (6,8,15,39), light intensity (1,5,23), DNA supercoiling (40), and the effects of the recently discovered pufQ gene (3,16). Relatively little attention has been paid to the interrelationships between heme and bacteriochlorophyll syntheses.…”

Section: Discussionmentioning

confidence: 99%

Isolation of a Rhodobacter capsulatus mutant that lacks c-type cytochromes and excretes porphyrins

Biel

1990

J Bacteriol

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A Rhodobacter capsulatus mutant lacking cytochrome oxidase activity was isolated by TnS mutagenesis. Difference spectroscopy of crude extracts and extracted c-type cytochromes demonstrated that this mutant completely lacked all c-type cytochromes. The strain did, however, synthesize normal amounts of b-type cytochromes and nonheme iron. This mutant also excreted large amounts of coproporphyrin and protoporphyrin and synthesized reduced amounts of bacteriochlorophyll, suggesting a link between the synthesis of c-type cytochromes and the expression of the tetrapyrrole biosynthetic pathway.The photosynthetic bacterium Rhodobacter capsulatus uses a single branched pathway to synthesize two major tetrapyrrole end products, heme and bacteriochlorophyll, and two minor tetrapyrrole end products, siroheme and vitamin B12. Since bacteriochlorophyll levels vary greatly with growth conditions, whereas heme levels remain relatively constant, some mechanism must exist to monitor and independently control the levels of these two tetrapyrroles. Studies in Rhodobacter sphaeroides have suggested that carbon flow over the common tetrapyrrole pathway leading to protoporphyrin is controlled by heme (25), and that heme may feedback inhibit aminolevulinate synthase (36). Recently, there have been some intriguing observations suggesting a link between cytochrome synthesis and pigment formation. Mutants lacking the R. capsulatus cytochrome be complex showed increased pigmentation (12), whereas mutants with reduced capacity to synthesize c-type cytochromes excreted an uncharacterized pigment (17). These observations suggest that the regulation of these two branches may be more complicated than previously thought. We attempted to probe the possible link between cytochrome c biosynthesis and expression of the tetrapyrrole pathway by isolating a mutant that completely lacks c-type cytochromes. Several years ago an R. capsulatus strain, MT113, was isolated (38) and subsequently shown to have reduced levels of all c-type cytochromes (13). This strain was isolated during a screen for normally pigmented mutants that lack cytochrome oxidase activity (38). In this report we describe the use of the cytochrome oxidase assay to isolate a TnS insertion mutant that completely lacks c-type cytochromes. In addition to lacking c-type cytochromes, this strain excretes coproporphyrin and protoporphyrin and synthesizes reduced amounts of bacteriochlorophyll. The isolation of this strain and the cloning of the gene responsible for the pleotropic phenotype will allow us to investigate the connection between cytochrome c synthesis and the expression of the tetrapyrrole biosynthetic pathway. sulfoxide. Escherichia coli was grown in L broth (4), which was modified by omitting glucose and decreasing the sodium chloride concentration to 0.5%. Solid media contained 1.5% agar (Difco). Antibiotics, when necessary, were added at the following final concentrations: kanamycin, 10 ,ug/ml; tetracycline, 1 pug/ml; spectinomycin, 5 ,ug/ml. Pigment determinations. Porphyrins...

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“…The biosynthesis of Bchl in both R. capsulatus and R. sphaeroides is known to be inhibited by high light intensities and by high oxygen tension (6,13,28,29). Yet, it has been shown that high oxygen tension does not repress transcription of bch genes to the same extent as oxygen represses transcription of thepuc,puh, andpufoperons (7,12,21,43).…”

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confidence: 99%

Recombinant expression of the pufQ gene of Rhodobacter capsulatus

et al. 1993

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Genetic studies have shown that the expression of the pufQ gene is required for normal levels of bacteriochlorophyll biosynthesis in Rhodobacter capsulatus. Yet, the exact function of the puJQ gene is unknown, and a puJQ gene product has never been isolated. We describe the recombinant overexpression of pufQ in Escherichia coli, as well as the purification and characterization of its gene product, the 74-amino-acid PufQ protein. Site-directed of R. capsulatus into operons and superoperons has recently been reviewed (37). The relative positions of the puf and puh operons and many of the bch and crt genes in the closely related bacterium Rhodobacter sphaeroides are similar to those found for the equivalent genes of R capsulatus (14). However, the distance between the puf and puh operons is some 10 kb shorter (40), and the photosynthetic gene cluster extends to include genes encoding other photosynthetic components, including cytochrome c2 (cycA) and the a-and 1-subunits of the B800-850 light-harvesting complex II (pucB and pucA, respectively, in the puc operon) (40).The biosynthesis of Bchl in both R. capsulatus and R.

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Regulation of tetrapyrrole synthesis by light in chemostat cultures of Rhodobacter sphaeroides

Cited by 12 publications

References 31 publications

Chlorophyll regulates accumulation of the plastid-encoded chlorophyll apoproteins CP43 and D1 by increasing apoprotein stability.

Chlorophyll regulates accumulation of the plastid-encoded chlorophyll apoproteins CP43 and D1 by increasing apoprotein stability.

Isolation of a Rhodobacter capsulatus mutant that lacks c-type cytochromes and excretes porphyrins

Recombinant expression of the pufQ gene of Rhodobacter capsulatus

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