3mas
From Proteopedia
Crystal structure of heterodimeric R132H mutant of human cytosolic NADP(+)-dependent isocitrate dehydrogenase in complex with NADP and isocitrate
Structural highlights
Disease[IDHC_HUMAN] Defects in IDH1 are involved in the development of glioma (GLM) [MIM:137800]. Gliomas are central nervous system neoplasms derived from glial cells and comprise astrocytomas, glioblastoma multiforme, oligodendrogliomas, and ependymomas. Note=Mutations affecting Arg-132 are tissue-specific, and suggest that this residue plays a unique role in the development of high-grade gliomas. Mutations of Arg-132 to Cys, His, Leu or Ser abolish magnesium binding and abolish the conversion of isocitrate to alpha-ketoglutarate. Instead, alpha-ketoglutarate is converted to R(-)-2-hydroxyglutarate. Elevated levels of R(-)-2-hydroxyglutarate are correlated with an elevated risk of malignant brain tumors. Publication Abstract from PubMedHuman cytosolic NADP-IDH (IDH1) has recently been found to be involved in tumorigenesis. Notably, the tumor-derived IDH1 mutations identified so far mainly occur at Arg132, and mutation R132H is the most prevalent one. This mutation impairs the oxidative IDH activity of the enzyme, but renders a new reduction function of converting alpha-ketoglutarate (alphaKG) to 2-hydroxyglutarate. Here, we report the structures of the R132H mutant IDH1 with and without isocitrate (ICT) bound. The structural data together with mutagenesis and biochemical data reveal a previously undefined initial ICT-binding state and demonstrate that IDH activity requires a conformational change to a closed pre-transition state. Arg132 plays multiple functional roles in the catalytic reaction; in particular, the R132H mutation hinders the conformational changes from the initial ICT-binding state to the pre-transition state, leading to the impairment of the IDH activity. Our results describe for the first time that there is an intermediate conformation that corresponds to an initial ICT-binding state and that the R132H mutation can trap the enzyme in this conformation, therefore shedding light on the molecular mechanism of the "off switch" of the potentially tumor-suppressive IDH activity. Furthermore, we proved the necessity of Tyr139 for the gained alphaKG reduction activity and propose that Tyr139 may play a vital role by compensating the increased negative charge on the C2 atom of alphaKG during the transfer of a hydride anion from NADPH to alphaKG, which provides new insights into the mechanism of the "on switch" of the hypothetically oncogenic reduction activity of IDH1 by this mutation. Molecular mechanisms of "off-on switch" of activities of human IDH1 by tumor-associated mutation R132H.,Yang B, Zhong C, Peng Y, Lai Z, Ding J Cell Res. 2010 Nov;20(11):1188-200. Epub 2010 Oct 26. PMID:20975740[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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