Inactivation of protein disulfide isomerase by alkylators including α,β-unsaturated aldehydes at low physiological pHs
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X.-W. Liu
Abstract
Protein disulfide isomerase (PDI) is known to contain the thioredoxin box motif with a low pKa cysteine residue. To investigate the reactivity of PDI with thiol modifiers at low physiological pHs, either the reduced (PDI[red]) or oxidized form (PDI[oxid]) of PDI was exposed to various alkylating ragents. When PDI was incubated with iodoacetamide at pH 6.3 for 30 min at 38C, a remarkable inactivation (>90%) of PDI[red] was caused by iodoacetamide (IC[50]=8 M). However, PDI[oxid] was only slightly inactivated (approximately 18%) by iodoacetamide. Similarly, PDI[red] was significantly inactivated by Nethylmaleimide (NEM), but PDI[oxid] was not. When the inactivation by these alkylators was analyzed by pseudofirst order kinetics, NEM (k[3]=1.7510[-2] s[-1]; K[i]=124 M) was observed to be more potent than iodoacetamide (k[3]=9.110[-3] s[-1]; K=311 M). Interestingly, the inactivation of PDI[red] by iodoacetamide was greater at pH 6.3 than pH 7.0, in contrast to a similar inactivation potency of NEM at both pHs. Moreover, the maximal inactivation of PDI[red] or PDI[oxid] by iodoacetamide was mainly observed around pH 6.0. In addition, PDI[red] was found to be inactivated by acrolein (IC[50]=10 M) at pH 6.3, and this inactivation was also greater at pH 6.3 than at pH 7. Based on these results, we suggest that PDI[red] is susceptible to inactivation by alkylators including endogenous α,β-unsaturated aldehydes at low physiological pHs.
Copyright © 2004 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- 55th Mosbach Colloquium: How nutrients influence gene activity
- Nutrient-gene interactions: a single nutrient and hundreds of target genes
- Regulation of gene expression by α-tocopherol
- Linking nutrition to genomics
- Metal-responsive transcription factor (MTF-1) and heavy metal stress response in Drosophila and mammalian cells: a functional comparison
- All-trans retinoic acid-responsive genes identified in the human SH-SY5Y neuroblastoma cell line and their regulated expression in the nervous system of early embryos
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- SMAD-signaling in chronic obstructive pulmonary disease: transcriptional down-regulation of inhibitory SMAD 6 and 7 by cigarette smoke
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