Dataset Information

Myo-inositol-1-phosphate synthase (Ino-1) functions as a protection mechanism in Corynebacterium glutamicum under oxidative stress.

ABSTRACT: Reactive oxygen species (ROS) generated in aerobic metabolism and oxidative stress lead to macromolecules damage, such as to proteins, lipids, and DNA, which can be eliminated by the redox buffer mycothiol (AcCys-GlcN-Ins, MSH). Myo-inositol-phosphate synthase (Ino-1) catalyzes the first committed step in the synthesis of MSH, thus playing a critical role in the growth of the organism. Although Ino-1s have been systematically studied in eukaryotes, their physiological and biochemical functions remain largely unknown in bacteria. In this study, we report that Ino-1 plays an important role in oxidative stress resistance in the gram-positive Actinobacteria Corynebacterium glutamicum. Deletion of the ino-1 gene resulted in a decrease in cell viability, an increase in ROS production, and the aggravation of protein carbonylation levels under various stress conditions. The physiological roles of Ino-1 in the resistance to oxidative stresses were corroborated by the absence of MSH in the ?ino-1 mutant. In addition, we found that the homologous expression of Ino-1 in C. glutamicum yielded a functionally active protein, while when expressed in Escherichia coliBL21(DE3), it lacked measurable activity. An examination of the molecular mass (Mr) suggested that Ino-1 expressed in E. coliBL21(DE3) was not folded in a catalytically competent conformation. Together, the results unequivocally showed that Ino-1 was important for the mediation of oxidative resistance by C. glutamicum.

SUBMITTER: Chen C

PROVIDER: S-EPMC6528642 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Myo-inositol-1-phosphate synthase (Ino-1) functions as a protection mechanism in Corynebacterium glutamicum under oxidative stress.

Chen Can C Chen Keqi K Su Tao T Zhang Bing B Li Guizhi G Pan Junfeng J Si Meiru M

MicrobiologyOpen 20181001 5

Reactive oxygen species (ROS) generated in aerobic metabolism and oxidative stress lead to macromolecules damage, such as to proteins, lipids, and DNA, which can be eliminated by the redox buffer mycothiol (AcCys-GlcN-Ins, MSH). Myo-inositol-phosphate synthase (Ino-1) catalyzes the first committed step in the synthesis of MSH, thus playing a critical role in the growth of the organism. Although Ino-1s have been systematically studied in eukaryotes, their physiological and biochemical functions r ...[more]

PMID: 30270521

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Project description:BACKGROUND:Phytic acid (InsP6) is considered as the major source of phosphorus and inositol phosphates in cereal grains. Reduction of phytic acid level in cereal grains is desirable in view of its antinutrient properties to maximize mineral bioavailability and minimize the load of phosphorus waste management. We report here RNAi mediated seed-specific silencing of myo-inositol-3-phosphate synthase (MIPS) gene catalyzing the first step of phytic acid biosynthesis in rice. Moreover, we also studied the possible implications of MIPS silencing on myo-inositol and related metabolism, since, first step of phytic acid biosynthesis is also the rate limiting step of myo-inositol synthesis, catalyzed by MIPS. RESULTS:The resulting transgenic rice plants (T3) showed a 4.59 fold down regulation in MIPS gene expression, which corresponds to a significant decrease in phytate levels and a simultaneous increment in the amount of inorganic phosphate in the seeds. A diminution in the myo-inositol content of transgenic plants was also observed due to disruption of the first step of phytic acid biosynthetic pathway, which further reduced the level of ascorbate and altered abscisic acid (ABA) sensitivity of the transgenic plants. In addition, our results shows that in the transgenic plants, the lower phytate levels has led to an increment of divalent cations, of which a 1.6 fold increase in the iron concentration in milled rice seeds was noteworthy. This increase could be attributed to reduced chelation of divalent metal (iron) cations, which may correlate to higher iron bioavailability in the endosperm of rice grains. CONCLUSION:The present study evidently suggests that seed-specific silencing of MIPS in transgenic rice plants can yield substantial reduction in levels of phytic acid along with an increase in inorganic phosphate content. However, it was also demonstrated that the low phytate seeds had an undesirable diminution in levels of myo-inositol and ascorbate, which probably led to sensitiveness of seeds to abscisic acid during germination. Therefore, it is suggested that though MIPS is the prime target for generation of low phytate transgenic plants, down-regulation of MIPS can have detrimental effect on myo-inositol synthesis and related pathways which are involved in key plant metabolism.

Project description:BackgroundThe eighth step of L-histidine biosynthesis is carried out by an enzyme called histidinol-phosphate phosphatase (HolPase). Three unrelated HolPase families are known so far. Two of them are well studied: HAD-type HolPases known from Gammaproteobacteria like Escherichia coli or Salmonella enterica and PHP-type HolPases known from yeast and Firmicutes like Bacillus subtilis. However, the third family of HolPases, the inositol monophosphatase (IMPase)-like HolPases, present in Actinobacteria like Corynebacterium glutamicum (HisN) and plants, are poorly characterized. Moreover, there exist several IMPase-like proteins in bacteria (e.g. CysQ, ImpA, and SuhB) which are very similar to HisN but most likely do not participate in L-histidine biosynthesis.ResultsDeletion of hisN, the gene encoding the IMPase-like HolPase in C. glutamicum, does not result in complete L-histidine auxotrophy. Out of four hisN homologs present in the genome of C. glutamicum (impA, suhB, cysQ, and cg0911), only cg0911 encodes an enzyme with HolPase activity. The enzymatic properties of HisN and Cg0911 were determined, delivering the first available kinetic data for IMPase-like HolPases. Additionally, we analyzed the amino acid sequences of potential HisN, ImpA, SuhB, CysQ and Cg0911 orthologs from bacteria and identified six conserved sequence motifs for each group of orthologs. Mutational studies confirmed the importance of a highly conserved aspartate residue accompanied by several aromatic amino acid residues present in motif 5 for HolPase activity. Several bacterial proteins containing all identified HolPase motifs, but showing only moderate sequence similarity to HisN from C. glutamicum, were experimentally confirmed as IMPase-like HolPases, demonstrating the value of the identified motifs. Based on the confirmed IMPase-like HolPases two profile Hidden Markov Models (HMMs) were build using an iterative approach. These HMMs allow the fast, reliable detection and differentiation of the two paralog groups from each other and other IMPases.ConclusionThe kinetic data obtained for HisN from C. glutamicum, as an example for an IMPase-like HolPases, shows remarkable differences in enzyme properties as compared to HAD- or PHP-type HolPases. The six sequence motifs and the HMMs presented in this study can be used to reliably differentiate between IMPase-like HolPases and IMPase-like proteins with no such activity, with the potential to enhance current and future genome annotations. A phylogenetic analysis reveals that IMPase-like HolPases are not only present in Actinobacteria and plant but can be found in further bacterial phyla, including, among others, Proteobacteria, Chlorobi and Planctomycetes.

Dataset Information

Myo-inositol-1-phosphate synthase (Ino-1) functions as a protection mechanism in Corynebacterium glutamicum under oxidative stress.

Publications

Myo-inositol-1-phosphate synthase (Ino-1) functions as a protection mechanism in Corynebacterium glutamicum under oxidative stress.

Similar Datasets

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