Nucleotide trapping

Smith AJ, van Helvoort A, van Meer G, Szabo K, Welker E, Szakacs G et al. MDR3 P-glycoprotein, a phosphatidylcholine translocase, transports several cytotoxic drugs and directly interacts with drugs as judged by interference with nucleotide trapping. J Biol Chem 2000 275(31) 23530—23539. 

Szabo K, Welker E, Bakos E, Muller M, Roninson I, Varadi A, Sarkadi B (1998) Drug-stimulated nucleotide trapping in the human multidrug transporter MDR1. Cooperation of the nucleotide binding domains. J Biol Chem 273 10132-10138... 

Terasaka, K., Shitan, N., Sato, R, Maniwa, R, Ueda, K. and Yazaki, Y. (2003) Application of vanadate-induced nucleotide trapping to plant cells for detection of ABC proteins. Plant Cell Physiol., 44,198-200. 

Ozvegy C, Varadi A, Sarkadi B. Characterization of drug transport, ATP hydrolysis, and nucleotide trapping by the human ABCG2 multidrug transporter. Modulation of substrate specificity by a point mutation. J Biol Chem 2002 277 47980-47990. 

Biochem. Pharmacol. 56, 719 (1998). Effect of Modulators on the ATPase Activity and Vanadate Nucleotide Trapping of Human P-Glycoprotein. 

Loo, T. W., Clarke, D. M., Vanadate trapping of nucleotide at the ATP-binding sites of human multidrug resistance P-glycoprotein exposes different residues to the drug-binding site, Proc. Natl. Acad. Sci. USA 2002, 99, 3511-3516. 

Electron donating a-substituents favour the non-Kolbe reaction but the radical intermediates in these anodic processes can be trapped during co-electrolysis with an alkanoic acid. Anodic decarboxylation of sugar uronic acids leads to formation of the radical which is very rapidly oxidised to a carbonium ion, stabilised by the adjacent ether group. However, in the presence of a tenfold excess of an alkanoic acid, the radical intermediate is trapped as the unsymmetrical coupling product [101]. Highly functionalised nucleotide derivatives such as 20 will couple successfully in the mixed Kolbe reaction [102], Other examples include the co-electrolysis of 3-oxa-alkanoic acids with an alkanoic acid [103] and the formation of 3-alkylindoles from indole-3-propanoic acid [104], Anodic oxidation of indole-3-propanoic acid alone gives no Kolbe dimer [105],... 

Sevilla et al. have shown that HO is not detected in relatively dry DNA (F < 8), but is detected in the F > 8 waters per nucleotide, suggesting that all holes do not transfer to DNA in the regime (8 > F > 22). The sites where these holes are initially produced are not particularly good hole traps. The holes move about until they encounter deep traps such as guanine. 

There has been continued interest in the radiation chemistry of the purines since early reports on oriented DNA by Graslund et al. [35] which suggest that the main trapping site of one-electron oxidation in DNA is the guanine base. It is remarkable that in aqueous solution, the electron adducts of the purine nucleosides and nucleotides undergo irreversible protonation at carbon with a rate constant 2 orders of magnitude higher than that for carbon protonation of the electron adduct in thymidine [36]. It is therefore important to know the properties of the various purine reduction products and to ask why they have not been observed in irradiated DNA. 

The value for imported nucleotide sugar is obtained by correcting the radioactivity associated with the pellet for the radioactivity trapped in the extravesicular space. 

---