Protein-sulfhydryl groups

Carraway, K.L., and Triplett, R.B. (1970) Reaction of carbodiimides with protein sulfhydryl groups. Biocbim. Biophys. Acta 200, 564-566. 

Luduena, R.F., Roach, M.C., Trcka, P.P., and Weintraub, S. (1982) Bioiodoacetyldithioethylamine A reversible cross-linking reagent for protein sulfhydryl group. Anal. Biochem. 117, 76. 

Intracellular and extracellular ROS activate tyrosine and serine-threonine kinases (i.e., the MAPK family members). Following TNF-a, TGF-f5 or EGF stimulation, intracellular ROS are generated which stimulate various signaling pathways [73], Tyrosine kinase receptors (e.g., EGF, PDGF and TGF-a) may be activated by ROS directly via protein sulfhydryl group modifications, or inhibition of phosphotyrosine phosphatases (PTPases) and subsequent receptor activation. The latter is possible as PTPases contain a redox-sensitive cysteine at their active site [78], and oxidation of protein sulfhydryl groups results in the inactivation of PTPases. 

Covalent protein adducts of quinones are formed through Mchael-type addihon reachon with protein sulfhydryl groups or glutathione. Metabolic activahon of several toxins (e.g., naphthalene, pentachlorophenol, and benzene) into quinones has been shown to result in protein quinone adducts (Lin et al, 1997 Rappaport et al, 1996 Zheng et al., 1997). Conversion of substituted hydroquinones such as p-aminophenol-hydroquinone and 2-bromo-hydroquinone to their respective glutathione S-conjugates must occur to allow bioactivation into nephrotoxic metabolites (Dekant, 1993). Western blot analysis of proteins from the kidneys of rats treated with 2-bromo-hydroquinone has revealed three distinct protein adducts conjugated to quinone-thioethers (Kleiner et al, 1998). 

Kluwe WM, McNish R, Smithson K, et al. 1981. Depletion by 1,2-dibromoethane, 1,2-dibromo-3-chloropropane, tris(2,3-dibromopropyl)phosphate, and hexachloro-1,3-butadiene of reduced non-protein sulfhydryl groups in target and non-target organs. Biochem Pharmacol 30 2265-2271. 

In Sprague-Dawley rats treated orally with 50, 75, 100 or 150 mg/kg bw acrylonitrile, hepatic nonprotein sulfhydryl concentration was significantly decreased after 30 min (Silver et al., 1982). Twenty-four hours after administration of 150 mg/kg bw, focal liver necrosis was observed. In isolated rat hepatocytes, acrylonitrile (1 mM) treatment resulted in the formation of thiobarbituric acid-positive products (a test for malon-aldehyde) and in depletion of non-protein sulfhydryl groups, but did not affect markedly the viability of the cells (Nerudova et al., 1988). 

Although batch and HTST pasteurization produces a cooked flavor in milk by activation of whey protein sulfhydryl groups, it is not severe... 

Giustarini D, Milzani A, Aldini G, Carini M, Rossi R, Dalle-Donne I. 2005. S-nitrosation versus S-glutathionylation of protein sulfhydryl groups by S-nitroso-glutathione. Antioxid Redox Signal 7 930-939. 

Inorganic selenium compounds are rather toxic, and probably attach to protein sulfhydryl groups, much like inorganic arsenic. In general, organoselenium compounds are regarded as less toxic than inorganic selenium compounds. 

Boyer, P. D. Spectrophotometric study of the reaction of protein sulfhydryl groups with organic mercurials. J. Am. Chem. Soc. 76, 4331—4337 (1954). 

It may seem odd that the technique of spectrophotometric titration, so extensively applied to the tyrosyl residues of proteins, has not been used in the study of protein sulfhydryl groups. The only study of this sort known to the author is the determination of the ionization constant of —SH grouj of thiolated gelatin (introduced by reaction with A -acetylhomocysteine thiolactone). By measuring the change in absorptivity as a function of pH at 2380 A, Benesch and Benesch (1958) found the apparent acidity of the thiol groups of the modified gelatin (pK = 9.8) to be nearly the same as that of an appropriate model compound, A -acetylhomocysteine (pK = 10.0). 

It should be noted that incomplete conversion of protein sulfhydryl groups to the mixed disulfide leaves open the possibility of intramolecular reactions leading to the formation of disulfide bonds. 

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