Cysteine cisplatin

Figure 2.5 The cisplatin reactive group can covalently couple to methionine-, cysteine-, and histidine-containing peptides or proteins. It also reacts with guanine groups to form a covalent modification on the N7 nitrogen.

Fumarase, inhibition by cisplatin, 37 195 Fumarate reductase cysteine distribution, 38 240-241 EPR, 47 452-456 ground-state properties, 47 23... 

P. Shearan, J. M. F. Alvarez, N. Zayed, and M. R. Smyth, HPI separation of cisplatin and its hydrolysis products on aluminudi and application to studies of their interaction with cysteine, Bio [ med. Chromatogr., 4 78 (1990). 

It was early determined that in the cell, the electrophilic species derived from cisplatin bind to three major targets RNA (which is present at high concentration in cytoplasm, together with nucleoproteins) (50%), DNA (40%) and proteins (10%) [25]. It also binds to cysteine and methionine residues of proteins, to metallothioneins, glutathione, methionine, and glutamate which are good traps for chloro and/or aqua platinum electrophiles [26],... 

XH- and 195Pt-NMR investigations have shown that therapeutic nucleophilic agents for cisplatin, such as Na(ddtc) (sodium diethyldithiocarba-mate) and thiourea, can help to remove Pt from certain proteins [35]. The mechanism may be based on the relatively easy reversal of Pt binding to methionine side chains. In contrast, nephrotoxicity, thought to be caused by formation of Pt-cysteine adducts (Pt11 thiolate bonds), cannot be reversed by Na(ddtc) and thiouera. 

Townsend DM and Flanigan MFI. Inhibition of gamma-glutamyl transpeptidase or cysteine S-conjugate beta-lyase activity blocks the nephrotoxicity of cisplatin in mice. The Journalof Pharmacology and Experimental Therapeutics 300 142-148,2002. 

Tumor cells with acquired resistance to cisplatin (a major clinical problem) are known to over-express metallothionein, a protein of —61 amino acids, of which 20 are cysteines. Metallothionein is involved with the natural metabolism of Zn(II) and Cu(I), and all the Cys sul-furs are involved in forming terminal or bridging bonds to the 7-10 metals that form clusters on the protein. Petering et al. (29) have recently shown that en is rapidly released from [Pt(en)Cl2] on reaction with metallothionein in vitro and that the rate-determining step does not involve aqua or hydroxo intermediates. 

Examples amphotericin B, aminoglycosides, cephaloridine, cisplatin, heavy metals, cysteine conjugates, 4-aminophenol, many others... 

Primary cultures of renal tubular, glomerular mesangial and endothelial cells from various species have been developed, including mouse [114], rat [115,116], rabbit [117] and pig [118]. Although cells in primary culture tend to dedifferentiate, the characteristics of those cells are usually closer to the in vivo situation than are animal cell lines, at least for a limited culture period. Primary cultures have been used successfully to study the short-term in vitro effects of cisplatin, gentamicin, cephalosporins, cysteine conjugates, butyl hydroperoxide, mercuric chloride, and cadmium chloride... 

A major component of the intracellular protein thiol pool is the class of inducible, cysteine-rich metallothionein (MT) proteins, important in heavy metal detoxification in eucaryotes (52). Studies of a human head and neck carcinoma cell line revealed no difference in nonprotein sulfhydryl content between parental cells and cells 30-fold resistant to cisplatin, but the latter had twofold greater levels of total protein sulfhydryl content (127). Several human and murine tumor cell lines resistant to cisplatin showed increased expression of one metallothionein, MT Ila, and increased levels of the protein (68). In addition, mouse cells transfected with the gene encoding metallothionein Ila showed a 10-fold increase in the level of MT accompanied by a 4.4-fold level of resistance to cw-DDP (68). By contrast, treatment of rats with cisplatin followed by chromatographic resolution of kidney metallothioneins showed that platinum did not elute with the MT fractions (84). Moreover, pretreatment of rats with Cd-" to induce MT production had no effect on the metabolism of platinum in kidney or liver (84). In vitro studies of the relative affinity of Cu-metallothionein for a variety of metal ions revealed very weak binding of divalent platinum... 

Au(Cl)(IPr)] and [Au(OH)(IPr)j were found to be more effective than complexes 53 and 54 bearing L-proline and L-cysteine ligands. These last two species interestingly gave the same dose response. However, complex 52 exhibited some toxicity. At a concentration below 2.5 pM no activity was observed with 53 and 54. In comparison, the cationic systems were active with IC50 below 1 pM. Further studies were undertaken on complexes 50, 51, 52, and 55, which were the most active, and compared to the less active system, 53 and 54 (Table 7.7). When tested on normal human urothelial cell line SV-HUC-1, bladder carcinoma cell line MGH-Ul, and breast cancer B42 CL16, the same trend was observed for the most efficient complexes. The comparison with cisplatin showed that the activities of these systems were lower by a factor of 20 to 100. 

The in vitro interactions of the cysteine-rich intracellular protein Zn7-metal-lothionein with cisplatin and transplatin and the histidine-rich proteins Hpni32,i33 HspA with a bismuth antiulcer compound were investigated, respectively. These kinds of interactions may play a crucial role in the metabolism of various metallodrugs. Notably, drug binding to plasma proteins has a strong influence on their biodistribution, biotransformation, and pharmacokinetics, and therefore merits further characterizations. 

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