| Structural highlights
Function
ICS1_ARATH Isochorismate synthase involved in the synthesis of salicylic acid (SA) required for both local and systemic acquired resistance (LAR and SAR) while SA synthesized through the phenylalanine ammonium lyase (PAL) pathway seems to potentiate plant cell death. Also involved in phylloquinone (vitamin K1) synthesis. Has no isochorismate pyruvate lyase (IPL) activity.[1] [2] [3] [4] [5]
Publication Abstract from PubMed
Salicylic acid (SA) plays a crucial role in plant defense against biotrophic and semi-biotrophic pathogens. In Arabidopsis (Arabidopsis thaliana), isochorismate synthase 1 (AtICS1) is a key enzyme for the pathogen-induced biosynthesis of SA via catalytic conversion of chorismate into isochorismate, an essential precursor for SA synthesis. Despite the extensive knowledge of ICS1-related menaquinone, siderophore, tryptophan (MST) enzymes in bacteria, the structural mechanisms for substrate binding and catalysis in plant isochorismate synthase (ICS) enzymes are unknown. This study reveals that plant ICS enzymes catalyze the isomerization of chorismate through a magnesium-dependent mechanism, with AtICS1 exhibiting the most substantial catalytic activity. Additionally, we present high-resolution crystal structures of apo AtICS1 and its complex with chorismate, offering detailed insights into the mechanisms of substrate recognition and catalysis. Importantly, our investigation indicates the existence of a potential substrate entrance channel and a gating mechanism regulating substrate into the catalytic site. Structural comparisons of AtICS1 with MST enzymes suggest a shared structural framework with conserved gating and catalytic mechanisms. This work provides valuable insights into the structural and regulatory mechanisms governing substrate delivery and catalysis in AtICS1, as well as other plant ICS enzymes.
Structural basis of chorismate isomerization by Arabidopsis ISOCHORISMATE SYNTHASE1.,Su Z, Niu C, Zhou S, Xu G, Zhu P, Fu Q, Zhang Y, Ming Z Plant Physiol. 2024 May 3:kiae260. doi: 10.1093/plphys/kiae260. PMID:38701037[6]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Nawrath C, Métraux JP. Salicylic acid induction-deficient mutants of Arabidopsis express PR-2 and PR-5 and accumulate high levels of camalexin after pathogen inoculation. Plant Cell. 1999 Aug;11(8):1393-404. PMID:10449575 doi:10.1105/tpc.11.8.1393
- ↑ Wildermuth MC, Dewdney J, Wu G, Ausubel FM. Isochorismate synthase is required to synthesize salicylic acid for plant defence. Nature. 2001 Nov 29;414(6863):562-5. PMID:11734859 doi:10.1038/35107108
- ↑ Gross J, Cho WK, Lezhneva L, Falk J, Krupinska K, Shinozaki K, Seki M, Herrmann RG, Meurer J. A plant locus essential for phylloquinone (vitamin K1) biosynthesis originated from a fusion of four eubacterial genes. J Biol Chem. 2006 Jun 23;281(25):17189-17196. PMID:16617180 doi:10.1074/jbc.M601754200
- ↑ Strawn MA, Marr SK, Inoue K, Inada N, Zubieta C, Wildermuth MC. Arabidopsis isochorismate synthase functional in pathogen-induced salicylate biosynthesis exhibits properties consistent with a role in diverse stress responses. J Biol Chem. 2007 Feb 23;282(8):5919-33. PMID:17190832 doi:10.1074/jbc.M605193200
- ↑ Garcion C, Lohmann A, Lamodière E, Catinot J, Buchala A, Doermann P, Métraux JP. Characterization and biological function of the ISOCHORISMATE SYNTHASE2 gene of Arabidopsis. Plant Physiol. 2008 Jul;147(3):1279-87. PMID:18451262 doi:10.1104/pp.108.119420
- ↑ Su Z, Niu C, Zhou S, Xu G, Zhu P, Fu Q, Zhang Y, Ming Z. Structural basis of chorismate isomerization by Arabidopsis ISOCHORISMATE SYNTHASE1. Plant Physiol. 2024 May 3:kiae260. PMID:38701037 doi:10.1093/plphys/kiae260
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