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Articles 1 - 12 of 12
Full-Text Articles in Molecular Biology
Putting Metal In The Middle, David Bollivar
Putting Metal In The Middle, David Bollivar
David Bollivar
Placing metal ions into the center of a porphyrin ring is a significant cellular challenge. Lundqvist et ai. (2010) provide snapshots of the AAA + motor unit of magnesium chelatase, an enzyme that insert magnesium ion into the porphyrin ring accompanied by ATP expenditure, in different states of binding to adenosyl nucleotides.
Recent Advances In Chlorophyll Biosynthesis, David Bollivar
Recent Advances In Chlorophyll Biosynthesis, David Bollivar
David Bollivar
The importance of chlorophyll (Chl) to the process of photosynthesis is obvious, and there is clear evidence that the regulation of Chl biosynthesis has a significant role in the regulation of assembly of the photosynthetic apparatus. The understanding of Chl biosynthesis has rapidly advanced in recent years. The identification of genetic loci associated with each of the biochemical steps has been accompanied by a greater appreciation of the role of Chl biosynthesis intermediates in intracellular signaling. The purpose of this review is to provide a source of information for all the steps in Chl and bacteriochlorophyll a biosynthesis, with an …
Rhodobacter Capsulatus Porphobilinogen Synthase, A High Activity Metal Ion Independent Hexamer, David W. Bollivar, Cheryl Clauson, Rachel Lighthall, Siiri Forbes, Bashkim Kokona, Robert Fairman, Lenka Kundrat, Eileen K. Jaffe
Rhodobacter Capsulatus Porphobilinogen Synthase, A High Activity Metal Ion Independent Hexamer, David W. Bollivar, Cheryl Clauson, Rachel Lighthall, Siiri Forbes, Bashkim Kokona, Robert Fairman, Lenka Kundrat, Eileen K. Jaffe
David Bollivar
Background: The enzyme porphobilinogen synthase (PBGS), which is central to the biosynthesis of heme, chlorophyll and cobalamins, has long been known to use a variety of metal ions and has recently been shown able to exist in two very different quaternary forms that are related to metal ion usage. This paper reports new information on the metal ion independence and quaternary structure of PBGS from the photosynthetic bacterium Rhodobacter capsulatus. Results: The gene for R. capsulatus PBGS was amplified from genomic DNA and sequencing revealed errors in the sequence database. R. capsulatus PBGS was heterologously expressed in E. coli and …
Genetic Analysis Of Chlorophyll Biosynthesis, David W. Bollivar, Jon Y. Suzuki, Carl E. Bauer
Genetic Analysis Of Chlorophyll Biosynthesis, David W. Bollivar, Jon Y. Suzuki, Carl E. Bauer
David Bollivar
During this decade, there have been major advancements in the understanding of genetic loci involved in synthesis of the family of Mg-tetrapyrroles known as chlorophylls and bacteriochlorophylls. Molecular genetic analysis of Mg-tetrapyrrole biosynthesis was initiated by the performance of detailed sequence and mutational analysis of the photosynthesis gene cluster from Rhodobacter capsulatus. These studies provided the first detailed understanding of genes involved in bacteriochlorophyll a biosynthesis. In the short time since these studies were initiated, most of the chlorophyll biosynthesis genes have been identified by virtue of their ability to complement bacteriochlorophyll a biosynthesis mutants as well as by sequence …
The Chlorophyll Biosynthetic Enzyme Mg-Protoporphyrin Ix Monomethyl Ester (Oxidative) Cyclase (Characterization And Partial Purification From Chlamydomonas Reinhardtii And Synechocystis Sp. Pcc 6803), David Bollivar
David Bollivar
A universal structural feature of chlorophyll molecules is the isocyclic ring. This ring is formed by the action of the enzyme Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase, which catalyzes a complex reaction in which Mg-protoporphyrin IX monomethyl ester is converted to divinyl protochlorophyllide (also called Mg-2,4-divinylpheoporphyrin a5), with the participation of NADPH and O2. Cyclase activity was demonstrated in lysed Chlamydomonas reinhardtii chloroplasts and extracts of Synechocystis sp. PCC 6803. The yield of the reaction product was increased by the addition of catalase and ascorbate or isoascorbate to the incubation mixture. These compounds may act by preventing degradation of the …
Anaerobic Protoporphyrin Biosynthesis Does Not Require Incorporation Of Methyl Groups From Methionine, David Bollivar, Thomas Elliott, Samuel I. Beale
Anaerobic Protoporphyrin Biosynthesis Does Not Require Incorporation Of Methyl Groups From Methionine, David Bollivar, Thomas Elliott, Samuel I. Beale
David Bollivar
It was recently reported (H. Akutsu, J.-S. Park, and S. Sano, J. Am. Chem. Soc. 115:12185–12186, 1993) that in the strict anaerobe methyl groups from exogenous L-methionine are incorporated specifically into the 1 and 3 positions (Fischer numbering system) on the heme groups of cytochrome c3. It was suggested that under anaerobic conditions, protoporphyrin IX biosynthesis proceeds via a novel pathway that does not involve coproporphyrinogen III as a precursor but instead may use precorrin-2 (1,3-dimethyluroporphyrinogen III), a siroheme and vitamin B12 precursor which is known to be derived from uroporphyrinogen III via methyl transfer from S-adenosyl-L-methionine. We have critically …
Formation Of The Isocyclic Ring Of Chlorophyll By Isolated Clamydomonas Reinhardtii Chloroplasts, David Bollivar, Samuel I. Beale
Formation Of The Isocyclic Ring Of Chlorophyll By Isolated Clamydomonas Reinhardtii Chloroplasts, David Bollivar, Samuel I. Beale
David Bollivar
Chlamydomonas reinhardtii chloroplasts catalyzed two sequential steps of Chl biosynthesis, S-adenosyl-L-methionine:Mg-protoporphyrin IX methyltransferase and Mg-protoporphyrin IX monomethyl ester oxidative cyclase. A double mutant strain of C. reinhardtii was constructed which has a cell wall deficiency and is unable to form chlorophyll in the dark. Dark-grown cells were disrupted with a BioNeb nebulizer under conditions which lysed the plasma membrane but not the chloroplast envelope. Chloroplasts were purified by Percoll density gradient centrifugation. The purified chloroplasts were used to define components required for the biosynthesis of Mg-2,4-divinylpheoporphyrin a 5 (divinyl protochlorophyllide) from Mg-protoporphyrin IX. Product formation requires the addition of Mg-protoporphyrin …
Molecular Genetic Analysis Of Terminal Steps In Bacteriochlorophyll A Biosynthesis: Characterization Of A Rhodobacter Capsulatus Strain That Synthesizes Geranylgeranoil-Esterified Bacteriochlorophyll A, David Bollivar, Shaojie Wang, James P. Allen, Carl E. Bauer
Molecular Genetic Analysis Of Terminal Steps In Bacteriochlorophyll A Biosynthesis: Characterization Of A Rhodobacter Capsulatus Strain That Synthesizes Geranylgeranoil-Esterified Bacteriochlorophyll A, David Bollivar, Shaojie Wang, James P. Allen, Carl E. Bauer
David Bollivar
Site-directed mutational analysis of the Rhodobacter capsulatus photosynthesis gene cluster was undertaken in order to identify and characterize genetic loci involved in bacteriochlorophyll a biosynthesis. A mutant in orf304 was shown to accumulate the tetrapyrrole intermediate "bacteriochlorophyllide a" which is a tetrapyrrole that has a bacteriochlorophyll a ring structure without the presence of an esterifying alcohol. A mutant in orf391 is shown to synthesize acteriochlorophyll a that is esterified with geranylgeraniol rather than the normal phytol. This latter result provides the first genetic confirmation that esterification of bacteriochlorophyllide a initially involves the addition of a geranylgeraniol group followed by sequential …
Heterologous Expression Of The Bchm Gene Product From Rhodobacter Capsulatus And Demonstration That It Encodes S-Adenosyl-L-Methionine: Mg-Protoporhyrin Ix Methyltransferase, David Bollivar, Ze-Yu Jiang, Carl E. Bauer, Samuel I. Beale
Heterologous Expression Of The Bchm Gene Product From Rhodobacter Capsulatus And Demonstration That It Encodes S-Adenosyl-L-Methionine: Mg-Protoporhyrin Ix Methyltransferase, David Bollivar, Ze-Yu Jiang, Carl E. Bauer, Samuel I. Beale
David Bollivar
The bacteriochlorophyll biosynthesis gene, bchM, from Rlodobacter capsulatus was previously believed to code for a polypeptide involved in formation of the cyclopentone ring of protochlorophyllide from Mg-protoporphyrin IX monomethyl ester. In this study, R. capsulatus bchM was expressed in Escherichia coli and the gene product was subsequently demonstrated by enzymatic analysis to catalyze methylation of Mg-protoporphyrin IX to form Mg-protoporphyrin IX monomethyl ester. Activity required the substrates Mg-protoporphyrin IX and S-adenosyl-L-methionine. 14C-labeled product was formed in incubations containing 14C-methyl-labeled S-adenosyl-L-methionine. On the basis of these and previous results, we also conclude that the bchH gene, which was previously reported to …
Genetic Analyses Of Photopigment Biosynthesis In Eubacteria: A Guiding Light For Algae And Plants, David Bollivar, Carl E. Bauer, Jon Y. Suzuki
Genetic Analyses Of Photopigment Biosynthesis In Eubacteria: A Guiding Light For Algae And Plants, David Bollivar, Carl E. Bauer, Jon Y. Suzuki
David Bollivar
A wide variety of macrocyclic tetrapyrrole compounds are synthesized by cells for use in diverse cellular processes. As shown in Fig. 1, this pathway includes the synthesis of closed tetrapyrrole compounds that contain metals, such as cobalt-containing cobalamin (vitamin B12), nickel-containing methanogenesis coenzyme F430, copper-containing pigment turacin, iron-containing heme and siroheme, and magnesium-containing chlorophylls and bacteriochlorophylls. Also synthesized by this pathway are a variety of open macrocyclic compounds such as the family of bilins that are used as a source of light-harvesting pigments in cyanobacteria, red algae, and cryptophytes as well as the chromophore that is covalently attached to phytochrome …
Association Of Tetrapyrrole Intermediates In The Bacteriochlorophyll A Biosynthetic Pathway With The Major Outer-Membrane Porin Protein Of Rhodobacter Capsulatus, David W. Bollivar, Carl E. Bauer
Association Of Tetrapyrrole Intermediates In The Bacteriochlorophyll A Biosynthetic Pathway With The Major Outer-Membrane Porin Protein Of Rhodobacter Capsulatus, David W. Bollivar, Carl E. Bauer
David Bollivar
Rhodobacter capsulatus regulates synthesis of bacteriochlorophyll a in response to changes in oxygen partial pressure and light intensity. One early model proposed that this regulation involved a carrier polypeptide that functions to tether tetrapyrrole intermediates to the membrane. In the present study we isolated tetrapyrrole intermediates accumulated in three strains of R. capsulatus that contain mutations which block bacteriochlorophyll a biosynthesis at different steps of the magnesium branch of the pathway. Each of the tetrapyrrole intermediates was shown to be associated with the same 32 kDa polypeptide, as indicated by similar electrophoretic mobility and antigenic cross-reactivity with polyclonal antisera. The …
Nucleotide Sequence Of S-Adenosyl-L-Methionine: Magnesium Protoporphyrin Methyltransferase From Rhodobacter Capsulatus, David W. Bollivar, Carl E. Bauer
Nucleotide Sequence Of S-Adenosyl-L-Methionine: Magnesium Protoporphyrin Methyltransferase From Rhodobacter Capsulatus, David W. Bollivar, Carl E. Bauer
David Bollivar
No abstract provided.