PubMed · 13494161
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E HANNIG, G LEUSCHNER. 1957. [Some alpha-alkylated basic propiophenones].. https://pubmed.ncbi.nlm.nih.gov/13494161/
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The reactivity of the episulfonium ion derived from S-(2-chloroethyl)glutathione (CEG), the glutathione conjugate of 1,2-dichloroethane, with the catalytic sites of protein disulfide isomerase (PDI) was investigated. The two cysteine residues of the two active sites of PDI are expected to be the major targets of alkylation. PDI was incubated with equimolar to 100-fold excess CEG. The activity of PDI was irreversibly inhibited with a concurrent loss of two thiols; however, PDI oxidative refolding activity was not completely inhibited. With mass spectrometry, sequencing PDI identified one alkylation event on each of the N-terminal cysteine residues in the two active site peptides. PDI appears robust and able to maintain some activity by steric constraint. We have established that the episulfonium ion of CEG can adduct PDI and may have important toxicologic significance for 1,2-dichloroethane toxicity.
A phenanthridinium-containing DNA building block was synthesized as an ethidium nucleoside analogue starting from 3,8-diamino-6-phenyl-phenanthridine. Using this building block, oligonucleotides bearing the phenanthridinium moiety as an artificial DNA base were prepared via automated solid-phase phosphoramidite chemistry. The modified phenanthridinium-containing DNA duplexes were characterized by UV/vis absorption spectroscopy (including the melting behavior), CD spectroscopy, and steady-state fluorescence spectroscopy. These experiments reveal the expected similarity of the synthetic phenanthridinium moiety with noncovalently bound ethidium. More importantly, the results show clearly that the artificial phenanthridinium base is intercalated within the DNA base stack. The counterbase as part of the complementary strand seems to have only a minor influence on the intercalation properties of the phenanthridinium moiety.
Protein tyrosine phosphatases (PTPs) constitute a large enzyme family with important biological functions. Inhibition of PTP activity through reversible oxidation of the active-site cysteine residue is emerging as a general, yet poorly characterized, regulatory mechanism. In this study, we describe a generic antibody-based method for detection of oxidation-inactivated PTPs. Previous observations of oxidation of receptor-like PTP (RPTP) alpha after treatment of cells with H(2)O(2) were confirmed. Platelet-derived growth factor (PDGF)-induced oxidation of endogenous SHP-2, sensitive to treatment with the phosphatidylinositol 3-kinase inhibitor LY294002, was demonstrated. Furthermore, oxidation of RPTPalpha was shown after UV-irradiation. Interestingly, the catalytically inactive second PTP domain of RPTPalpha demonstrated higher susceptibility to oxidation. The experiments thus demonstrate previously unrecognized intrinsic differences between PTP domains to susceptibility to oxidation and suggest mechanisms for regulation of RPTPs with tandem PTP domains. The antibody strategy for detection of reversible oxidation is likely to facilitate further studies on regulation of PTPs and might be applicable to analysis of redox regulation of other enzyme families with active-site cysteine residues.