An isochorismate hydroxymutase isogene in <i>Escherichia coli</i>

Müller, Rolf; Dahm, Claudia; Schulte, Gaby; Leistner, Eckhard

doi:10.1016/0014-5793(95)01436-5

Cited by 25 publications

(13 citation statements)

References 27 publications

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“…This medium contains a dye that forms an intense blue complex with iron and turns orange when iron has been transferred to another ironbinding molecule. For our functional assay, we used PBB8, a mutant of E. coli that lacks endogenous ICS activity and is therefore unable to produce enterobactin (Muller et al, 1996;Fig. 3).…”

Section: Subcellular Localization Of Ics1 and Ics2mentioning

confidence: 99%

Characterization and Biological Function of the ISOCHORISMATE SYNTHASE2 Gene of Arabidopsis

et al. 2008

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Section: Subcellular Localization Of Ics1 and Ics2mentioning

confidence: 99%

Characterization and Biological Function of the ISOCHORISMATE SYNTHASE2 Gene of Arabidopsis

et al. 2008

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“…On the other hand, as shown in Fig. 1, bacterial synthesis of menaquinones occurs via the intermediates ortho-succinyl benzoate and 1,4-dihydroxy-2-naphthoate (NA) (11). Although bi-(or multi-) functional bacterial ICS enzymes associated with synthesis of ortho-succinyl benzoate have not been reported, eubacterial genomes contain conserved colocalized MenF (ICS) and MenD (2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase) genes (12) to channel IC to the menaquinone pathway (e.g.…”

mentioning

confidence: 99%

Arabidopsis Isochorismate Synthase Functional in Pathogen-induced Salicylate Biosynthesis Exhibits Properties Consistent with a Role in Diverse Stress Responses

Strawn

Marr

Inoue

et al. 2007

Journal of Biological Chemistry

220

146

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Salicylic acid (SA) is a phytohormone best known for its role in plant defense. It is synthesized in response to diverse pathogens and responsible for the large scale transcriptional induction of defense-related genes and the establishment of systemic acquired resistance. Surprisingly, given its importance in plant defense, an understanding of the underlying enzymology is lacking. In Arabidopsis thaliana, the pathogen-induced accumulation of SA requires isochorismate synthase (AtICS1). Here, we show that AtICS1 is a plastid-localized, stromal protein using chloroplast import assays and immunolocalization. AtICS1 acts as a monofunctional isochorismate synthase (ICS), catalyzing the conversion of chorismate to isochorismate (IC) in a reaction that operates near equilibrium (K eq ‫؍‬ 0.89). It does not convert chorismate directly to SA (via an IC intermediate) as does Yersinia enterocolitica Irp9. Using an irreversible coupled spectrophotometric assay, we found that AtICS1 exhibits an apparent K m of 41.5 M and k cat ‫؍‬ 38.7 min ؊1 for chorismate. This affinity for chorismate would allow it to successfully compete with other pathogen-induced, chorismate-utilizing enzymes. Furthermore, the biochemical properties of AtICS1 indicate its activity is not regulated by light-dependent changes in stromal pH, Mg 2؉ , or redox and that it is remarkably active at 4°C consistent with a role for SA in cold-tolerant growth. Finally, our analyses support plastidic synthesis of stress-induced SA with the requirement for one or more additional enzymes responsible for the conversion of IC to SA, because non-enzymatic conversion of IC to SA under physiological conditions was negligible.

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“…Most microorganisms contain two distinct ICS genes: menF is involved in biosynthesis of menaquinones (vitamin K2) for anaerobic electron transport (3), and entC is associated with aerobic metabolism for the production of iron chelators, such as 2,3-dihydroxybenzoic acid (2,3-DHBA), salicylic acid (SA), and complex siderophores, e.g., enterobactin and pyochelin (1,4). ICS has also been associated with two distinct functions in plants ( Fig.…”

mentioning

confidence: 99%

Alternative splicing and gene duplication differentially shaped the regulation of isochorismate synthase in Populus and Arabidopsis

Yuan

Chung

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Isochorismate synthase (ICS) converts chorismate to isochorismate for the biosynthesis of phylloquinone, an essential cofactor for photosynthetic electron transport. ICS is also required for salicylic acid (SA) synthesis during Arabidopsis defense. In several other species, including Populus, SA is derived primarily from the phenylpropanoid pathway. We therefore sought to investigate ICS regulation in Populus to learn the extent of ICS involvement in SA synthesis and defense. Arabidopsis harbors duplicated AtICS genes that differ in their exon-intron structure, basal expression, and stress inducibility. In contrast, we found a single ICS gene in Populus and six other sequenced plant genomes, pointing to the AtICS duplication as a lineage-specific event. The Populus ICS encodes a functional plastidic enzyme, and was not responsive to stresses that stimulated phenylpropanoid accumulation. Populus ICS underwent extensive alternative splicing that was rare for the duplicated AtICSs. Sequencing of 184 RT-PCR Populus clones revealed 37 alternative splice variants, with normal transcripts representing Ϸ50% of the population. When expressed in Arabidopsis, Populus ICS again underwent alternative splicing, but did not produce normal transcripts to complement AtICS1 function. The splice-site sequences of Populus ICS are unusual, suggesting a causal link between junction sequence, alternative splicing, and ICS function. We propose that gene duplication and alternative splicing of ICS evolved independently in Arabidopsis and Populus in accordance with their distinct defense strategies. AtICS1 represents a divergent isoform for inducible SA synthesis during defense. Populus ICS primarily functions in phylloquinone biosynthesis, a process that can be sustained at low ICS transcript levels.defense ͉ phenylpropanoid ͉ splice site sequence ͉ phylloquinone ͉ salicylic acid

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An isochorismate hydroxymutase isogene in Escherichia coli

Cited by 25 publications

References 27 publications

Characterization and Biological Function of the ISOCHORISMATE SYNTHASE2 Gene of Arabidopsis

Characterization and Biological Function of the ISOCHORISMATE SYNTHASE2 Gene of Arabidopsis

Arabidopsis Isochorismate Synthase Functional in Pathogen-induced Salicylate Biosynthesis Exhibits Properties Consistent with a Role in Diverse Stress Responses

Alternative splicing and gene duplication differentially shaped the regulation of isochorismate synthase in Populus and Arabidopsis

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