scholarly journals Localization of Mg-Chelatase and Mg-Protoporphyrin IX Monomethyl Ester (Oxidative) Cyclase Activities within Isolated, Developing Cucumber Chloroplasts

1984 ◽  
Vol 75 (3) ◽  
pp. 662-664 ◽  
Author(s):  
Thomas P. Fuesler ◽  
Yum-Shing Wong ◽  
Paul A. Castelfranco
Keyword(s):  
Protoporphyrin Ix ◽  
Mg Chelatase ◽  
Monomethyl Ester

Mutation in Mg-Protoporphyrin IX Monomethyl Ester Cyclase Causes Yellow and Spotted Leaf Phenotype in Rice

2019 ◽  
Vol 37 (4) ◽  
pp. 253-264 ◽  
Author(s):  
Chun Li ◽  
Furong Ma ◽  
Renjun Jiao ◽  
Congping Chen ◽  
Qian Wang ◽  
...  
Keyword(s):  
Protoporphyrin Ix ◽  
Leaf Phenotype ◽  
Monomethyl Ester

scholarly journals The Ycf54 protein is part of the membrane component of Mg-protoporphyrin IX monomethyl ester cyclase from barley (Hordeum vulgareL.)

FEBS Journal ◽  
2014 ◽  
Vol 281 (10) ◽  
pp. 2377-2386 ◽  
Author(s):  
David Bollivar ◽  
Ilka Braumann ◽  
Kasper Berendt ◽  
Simon P. Gough ◽  
Mats Hansson
Keyword(s):  
Protoporphyrin Ix ◽  
Membrane Component ◽  
Monomethyl Ester

scholarly journals Further observations on the Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase system

1993 ◽  
Vol 290 (2) ◽  
pp. 355-359 ◽  
Author(s):  
B J Whyte ◽  
P A Castelfranco
Keyword(s):  
Pentose Phosphate Pathway ◽  
Protoporphyrin Ix ◽  
Companion Paper ◽  
Pentose Phosphate ◽  
Chloroplast Pigments ◽  
Cyclization Process ◽  
Reconstituted System ◽  
Sugar Phosphates ◽  
Cytochrome P 450 ◽  
Monomethyl Ester

The Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase was strongly inhibited by CN- and N3- in a reconstituted system, but was inhibited slightly or not at all by the same reagents in intact developing chloroplasts. Known inhibitors of cytochrome P-450 processes showed no consistent effect. Benzoquinone and quinol, which can give rise to the same semiquinone by one-electron redox events, were strong inhibitors of the cyclase. It was previously shown that O2 and a source of electrons are required in the cyclization process. The substrates for the dehydrogenases of the pentose phosphate pathway (glucose 6-phosphate and 6-phosphogluconate) were effective reductants in the reconstituted system with supernatant that had been dialysed or passed through Sephadex G-50, in the absence of added NADP+. However, inhibitor studies suggested that the electrons from these sugar phosphates reached the cyclase system via NADPH. Therefore we infer the presence of protein-bound NADP+ that can be reduced by glucose 6-phosphate and 6-phosphogluconate and donate reducing equivalents to the cyclase system. This bound NADPH pool may be particularly effective in the cyclization process, owing to channeling. These findings are discussed in relation to the results of a companion paper [Whyte and Castelfranco (1993) Biochem. J. 290, 361-367] on the breakdown of chloroplast pigments in the same reconstituted system.

scholarly journals Mg-chelatase I subunit 1 and Mg-protoporphyrin IX methyltransferase affect the stomatal aperture in Arabidopsis thaliana

2014 ◽  
Vol 127 (4) ◽  
pp. 553-563 ◽  
Author(s):  
Masakazu Tomiyama ◽  
Shin-ichiro Inoue ◽  
Tomo Tsuzuki ◽  
Midori Soda ◽  
Sayuri Morimoto ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Protoporphyrin Ix ◽  
Stomatal Aperture ◽  
Mg Chelatase

Chlorophyll a biosynthesis

1976 ◽  
Vol 273 (924) ◽  
pp. 207-225 ◽  
Keyword(s):  
Chlorophyll A ◽  
Chlorophyll Biosynthesis ◽  
Protoporphyrin Ix ◽  
Chlorophyll Synthesis ◽  
Synthesis Reaction ◽  
Etiolated Leaves ◽  
Regulatory Aspects ◽  
Vinyl Group ◽  
Chlorophyll A Biosynthesis ◽  
Monomethyl Ester

Protoporphyrin IX is believed to be an intermediate common to both haem and chlorophyll biosynthesis. The pathway specific to chlorophyll starts with magnesium protoporphyrin and its monomethyl ester. Two routes have been proposed for conversion of the latter compound to protochlorophyllide: A, formation of the isocyclic ring followed by reduction of the 4-vinyl group, or B, reduction of the 4-vinyl group followed by formation of the isocyclic ring. Membranes prepared from isolated barley etioplasts are found to convert magnesium 2,4-divinylphaeoporphyrin a 5 monomethyl ester to chlorophyllide a at a rate equal to that of chlorophyll synthesis in intact leaves: this result supports route A. NADPH is necessary to maintain the two successive reductive steps: reduction of the 4-vinyl group and then the photoreduction of ring IV to yield chlorophyllide. The prohaem content of etiolated leaves does not increase during the phase of active chlorophyll synthesis although evidence is presented that suggests that the ALA synthesis reaction that regulates chlorophyll synthesis is common to both pathways. This and other regulatory aspects are discussed.

1-N-histidine phosphorylation of ChlD by the AAA+ ChlI2 stimulates magnesium chelatase activity in chlorophyll synthesis

2017 ◽  
Vol 474 (12) ◽  
pp. 2095-2105 ◽  
Author(s):  
Artur Sawicki ◽  
Shuaixiang Zhou ◽  
Kathrin Kwiatkowski ◽  
Meizhong Luo ◽  
Robert D. Willows
Keyword(s):  
Rhodobacter Capsulatus ◽  
Protoporphyrin Ix ◽  
Chlorophyll Synthesis ◽  
Magnesium Chelatase ◽  
Orthologous Protein ◽  
Substrate Complex ◽  
Motor Complex ◽  
Histidine Phosphorylation ◽  
Mg Chelatase ◽  
Stimulation Of

Magnesium chelatase (Mg-chelatase) inserts magnesium into protoporphyrin during the biosynthesis of chlorophyll and bacteriochlorophyll. Enzyme activity is reconstituted by forming two separate preactivated complexes consisting of a GUN4/ChlH/protoporphyrin IX substrate complex and a ChlI/ChlD enzyme ‘motor’ complex. Formation of the ChlI/ChlD complex in both Chlamydomonas reinhardtii and Oryza sativa is accompanied by phosphorylation of ChlD by ChlI, but the orthologous protein complex from Rhodobacter capsulatus, BchI/BchD, gives no detectable phosphorylation of BchD. Phosphorylation produces a 1-N-phospho-histidine within ChlD. Proteomic analysis indicates that phosphorylation occurs at a conserved His residue in the C-terminal integrin I domain of ChlD. Comparative analysis of the ChlD phosphorylation with enzyme activities of various ChlI/ChlD complexes correlates the phosphorylation by ChlI2 with stimulation of Mg-chelatase activity. Mutation of the H641 of CrChlD to E641 prevents both phosphorylation and stimulation of Mg-chelatase activity, confirming that phosphorylation at H641 stimulates Mg-chelatase. The properties of ChlI2 compared with ChlI1 of Chlamydomonas and with ChlI of Oryza, shows that ChlI2 has a regulatory role in Chlamydomonas.

scholarly journals Structure of GUN4 fromChlamydomonas reinhardtii

2015 ◽  
Vol 71 (8) ◽  
pp. 1094-1099 ◽  
Author(s):  
Shabnam Tarahi Tabrizi ◽  
David B. Langley ◽  
Stephen J. Harrop ◽  
Anthony P. Duff ◽  
Robert D. Willows
Keyword(s):  
Crystal Structure ◽  
Chlamydomonas Reinhardtii ◽  
Chlorophyll Biosynthesis ◽  
Conformational Dynamics ◽  
Protoporphyrin Ix ◽  
Biosynthesis Pathway ◽  
Broad Agreement ◽  
Binding Cleft ◽  
Mg Chelatase

The genomes uncoupled 4 (GUN4) protein stimulates chlorophyll biosynthesis by increasing the activity of Mg-chelatase, the enzyme that inserts magnesium into protoporphyrin IX (PPIX) in the chlorophyll biosynthesis pathway. One of the roles of GUN4 is in binding PPIX and Mg-PPIX. In eukaryotes, GUN4 also participates in plastid-to-nucleus signalling, although the mechanism for this is unclear. Here, the first crystal structure of a eukaryotic GUN4, fromChlamydomonas reinhardtii, is presented. The structure is in broad agreement with those of previously solved cyanobacterial structures. Most interestingly, conformational divergence is restricted to several loops which cover the porphyrin-binding cleft. The conformational dynamics suggested by this ensemble of structures lend support to the understanding of how GUN4 binds PPIX or Mg-PPIX.

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