Dataset Information

S-adenosylmethionine synthases in plants: Structural characterization of type I and II isoenzymes from Arabidopsis thaliana and Medicago truncatula.

ABSTRACT: S-adenosylmethionine synthases (MATs) are responsible for production of S-adenosylmethionine, the cofactor essential for various methylation reactions, production of polyamines and phytohormone ethylene, etc. Plants have two distinct MAT types (I and II). This work presents the structural analysis of MATs from Arabidopsis thaliana (AtMAT1 and AtMAT2, both type I) and Medicago truncatula (MtMAT3a, type II), which, unlike most MATs from other domains of life, are dimers where three-domain subunits are sandwiched flat with one another. Although MAT types are very similar, their subunits are differently oriented within the dimer. Structural snapshots along the enzymatic reaction reveal the exact conformation of precatalytic methionine in the active site and show a binding niche, characteristic only for plant MATs, that may serve as a lock of the gate loop. Nevertheless, plants, in contrary to mammals, lack the MAT regulatory subunit, and the regulation of plant MAT activity is still puzzling. Our structures open a possibility of an allosteric activity regulation of type I plant MATs by linear compounds, like polyamines, which would tighten the relationship between S-adenosylmethionine and polyamine biosynthesis.

SUBMITTER: Sekula B

PROVIDER: S-EPMC8456715 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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S-adenosylmethionine synthases in plants: Structural characterization of type I and II isoenzymes from Arabidopsis thaliana and Medicago truncatula.

Sekula Bartosz B Ruszkowski Milosz M Dauter Zbigniew Z

International journal of biological macromolecules 20200211

S-adenosylmethionine synthases (MATs) are responsible for production of S-adenosylmethionine, the cofactor essential for various methylation reactions, production of polyamines and phytohormone ethylene, etc. Plants have two distinct MAT types (I and II). This work presents the structural analysis of MATs from Arabidopsis thaliana (AtMAT1 and AtMAT2, both type I) and Medicago truncatula (MtMAT3a, type II), which, unlike most MATs from other domains of life, are dimers where three-domain subunits ...[more]

PMID: 32057875

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Project description:Cytidine triphosphate (CTP) is essential for DNA, RNA and phospholipid biosynthesis. De novo synthesis is catalyzed by CTP synthases (CTPS). Arabidopsis encodes five CTPS isoforms that unanimously share conserved motifs found across kingdoms, suggesting all five are functional enzymes. Whereas CTPS1-4 are expressed throughout Arabidopsis tissues, CTPS5 reveals exclusive expression in developing embryos. CTPS activity and substrates affinities were determined for a representative plant enzyme on purified recombinant CTPS3 protein. As demonstrated in model organisms such as yeast, fruit fly and mammals, CTPS show the capacity to assemble into large filaments called cytoophidia. Transient expression of N- and C-terminal YFP-CTPS fusion proteins in Nicotiana benthamiana allowed to monitor such filament formation. Interestingly, CTPS1 and 2 always appeared as soluble proteins, whereas filaments were observed for CTPS3, 4 and 5 independent of the YFP-tag location. However, when similar constructs were expressed in Saccharomyces cerevisiae, no filaments were observed, pointing to a requirement for organism-specific factors in vivo. Indications for filament assembly were also obtained in vitro when recombinant CTPS3 protein was incubated in the presence of CTP. T-DNA-insertion mutants in four CTPS loci revealed no apparent phenotypical alteration. In contrast, CTPS2 T-DNA-insertion mutants did not produce homozygous progenies. An initial characterization of the CTPS protein family members from Arabidopsis is presented. We provide evidence for their involvement in nucleotide de novo synthesis and show that only three of the five CTPS isoforms were able to form filamentous structures in the transient tobacco expression system. This represents a striking difference from previous observations in prokaryotes, yeast, Drosophila and mammalian cells. This finding will be highly valuable to further understand the role of filament formation to regulate CTPS activity.

Dataset Information

S-adenosylmethionine synthases in plants: Structural characterization of type I and II isoenzymes from Arabidopsis thaliana and Medicago truncatula.

Publications

S-adenosylmethionine synthases in plants: Structural characterization of type I and II isoenzymes from Arabidopsis thaliana and Medicago truncatula.

Similar Datasets

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