GUN4-Protoporphyrin IX Is a Singlet Oxygen Generator with Consequences for Plastid Retrograde Signaling

Tabrizi, Shabnam Tarahi; Sawicki, Artur; Zhou, Shuaixiang; Luo, Meizhong; Willows, Robert D.

doi:10.1074/jbc.c116.719989

Cited by 39 publications

(25 citation statements)

References 42 publications

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“…Gun4 lowers the magnesium concentration required for chelatase activity at low porphyrin concentrations (185) and substantially enhances the catalytic rate, by at least ten-fold (181). There are structures of apo-ChlH (186), apo-Gun4 (185,187,188), and Synechocystis sp. PCC 6803 Gun4 bound to both deuteroporphyrin (DIX) and Mgdeuteroporphyrin (Mg-DIX) (189); however, structures of sub-complexes, and the entire Mg chelatase complex at various stages of the catalytic cycle, will be required for a complete characterization of this important enzyme complex.…”

Section: The Transformation Of Protoix Into Chls -Chl Amentioning

confidence: 99%

Biosynthesis of the modified tetrapyrroles—the pigments of life

Bryant

Hunter

Warren

2020

Journal of Biological Chemistry

188

164

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Modified tetrapyrroles are large macrocyclic compounds, consisting of diverse conjugation and metal chelation systems and imparting an array of colors to the biological structures that contain them. Tetrapyrroles represent some of the most complex small molecules synthesized by cells and are involved in many essential processes that are fundamental to life on Earth, including photosynthesis, respiration, and catalysis. These molecules are all derived from a common template through a series of enzyme-mediated transformations that alter the oxidation state of the macrocycle and also modify its size, its side-chain composition, and the nature of the centrally chelated metal ion. The different modified tetrapyrroles include chlorophylls, hemes, siroheme, corrins (including vitamin B12), coenzyme F430, heme d1, and bilins. After nearly a century of study, almost all of the more than 90 different enzymes that synthesize this family of compounds are now known, and expression of reconstructed operons in heterologous hosts has confirmed that most pathways are complete. Aside from the highly diverse nature of the chemical reactions catalyzed, an interesting aspect of comparative biochemistry is to see how different enzymes and even entire pathways have evolved to perform alternative chemical reactions to produce the same end products in the presence and absence of oxygen. Although there is still much to learn, our current understanding of tetrapyrrole biogenesis represents a remarkable biochemical milestone that is summarized in this review.

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Section: The Transformation Of Protoix Into Chls -Chl Amentioning

confidence: 99%

Biosynthesis of the modified tetrapyrroles—the pigments of life

Bryant

Hunter

Warren

2020

Journal of Biological Chemistry

188

164

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“…Alternatively, the EX1 pathway might be important in plant defense against pathogens [402,430]. 1 O 2 produced by Chl catabolites has been proposed to be involved in the hypersensitive response [431], and similarly to the flu-mutant [115], 1 O 2 produced by Chl catabolites has been suggested to initiate the EX1 pathway also in the wild type [432]. Interestingly, NADPH-protochlorophyllide oxidoreductases were shown to associate with EX1 and FtsH [425], though the interactions may be weak or transient, as they are not always observed [433].…”

Section: Signaling By 1 Omentioning

confidence: 99%

Oxygen and ROS in Photosynthesis

Khorobrykh

Havurinne

Mattila

et al. 2020

Plants

187

133

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Oxygen is a natural acceptor of electrons in the respiratory pathway of aerobic organisms and in many other biochemical reactions. Aerobic metabolism is always associated with the formation of reactive oxygen species (ROS). ROS may damage biomolecules but are also involved in regulatory functions of photosynthetic organisms. This review presents the main properties of ROS, the formation of ROS in the photosynthetic electron transport chain and in the stroma of chloroplasts, and ROS scavenging systems of thylakoid membrane and stroma. Effects of ROS on the photosynthetic apparatus and their roles in redox signaling are discussed.

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“…GUN4 was demonstrated to shield porphyrins from collisions with molecular oxygen that produce 1 O 2 ( Brzezowski et al, 2014 ), as was suggested previously ( Larkin et al, 2003 ; Verdecia et al, 2005 ). However, the subsequent finding that porphyrin-binding pocket of GUN4 is partially opened ( Chen et al, 2015 ) and that in vitro , porphyrins produce more 1 O 2 when they are bound to GUN4 ( Tarahi Tabrizi et al, 2016 ) indicates that GUN4 requires additional factors to shield porphyrins from collisions with molecular oxygen. Thus, GUN4 and GUN5 divert protoporphyrin IX from heme biosynthesis to chlorophyll biosynthesis by inserting a magnesium ion into protoporphyrin IX, yielding Mg-Proto.…”

Section: Gun2 Gun3 Gun4 Gun5 and Gun6mentioning

confidence: 99%

Tetrapyrrole Signaling in Plants

Larkin

2016

Front. Plant Sci.

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Tetrapyrroles make critical contributions to a number of important processes in diverse organisms. In plants, tetrapyrroles are essential for light signaling, the detoxification of reactive oxygen species, the assimilation of nitrate and sulfate, respiration, photosynthesis, and programed cell death. The misregulation of tetrapyrrole metabolism can produce toxic reactive oxygen species. Thus, it is not surprising that tetrapyrrole metabolism is strictly regulated and that tetrapyrrole metabolism affects signaling mechanisms that regulate gene expression. In plants and algae, tetrapyrroles are synthesized in plastids and were some of the first plastid signals demonstrated to regulate nuclear gene expression. In plants, the mechanism of tetrapyrrole-dependent plastid-to-nucleus signaling remains poorly understood. Additionally, some of experiments that tested ideas for possible signaling mechanisms appeared to produce conflicting data. In some instances, these conflicts are potentially explained by different experimental conditions. Although the biological function of tetrapyrrole signaling is poorly understood, there is compelling evidence that this signaling is significant. Specifically, this signaling appears to affect the accumulation of starch and may promote abiotic stress tolerance. Tetrapyrrole-dependent plastid-to-nucleus signaling interacts with a distinct plastid-to-nucleus signaling mechanism that depends on GENOMES UNCUOPLED1 (GUN1). GUN1 contributes to a variety of processes, such as chloroplast biogenesis, the circadian rhythm, abiotic stress tolerance, and development. Thus, the contribution of tetrapyrrole signaling to plant function is potentially broader than we currently appreciate. In this review, I discuss these aspects of tetrapyrrole signaling.

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GUN4-Protoporphyrin IX Is a Singlet Oxygen Generator with Consequences for Plastid Retrograde Signaling

Cited by 39 publications

References 42 publications

Biosynthesis of the modified tetrapyrroles—the pigments of life

Biosynthesis of the modified tetrapyrroles—the pigments of life

Oxygen and ROS in Photosynthesis

Tetrapyrrole Signaling in Plants

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