Proteins alkylation

Thompson, D. C. Perera, K. London, R. Spontaneous hydrolysis of 4-trifluoromethyl-phenol to a quinone methide and subsequent protein alkylation. Chem.-Biol. Interact. 2000, 126, 1-14. 

An affinity label is a molecule that contains a functionality that is chemically reactive and will therefore form a covalent bond with other molecules containing a complementary functionality. Generally, affinity labels contain electrophilic functionalities that form covalent bonds with protein nucleophiles, leading to protein alkylation or protein acylation. In some cases affinity labels interact selectively with specific amino acid side chains, and this feature of the molecule can make them useful reagents for defining the importance of certain amino acid types in enzyme function. For example, iodoacetate and A-ethyl maleimide are two compounds that selectively modify the sulfur atom of cysteine side chains. These compounds can therefore be used to test the functional importance of cysteine residues for an enzyme s activity. This topic is covered in more detail below in Section 8.4. 

A particularly attractive feature of acridine (80d) is that this compound can be tracked through the parasite using confocal microscopy and this has enabled O Neill and coworkers to determine intraparasitic sites of protein alkylation". ... 

An additional step in the radical mechanism has been suggested namely, that collapse of C-4 radical intermediate 234 to a neutral but highly reactive alkoxy-epoxide 235 occurs (Scheme 5).104 Protein alkylation then presumably occurs via 235 and not radical intermediates such as 234. Unfortunately, epoxide 235 is probably too unstable to be handled or identified. In the case of 258 however, we were granted the opportunity to test the hypothesis that an intermediate epoxide was responsible for the mode of action. Of the series of three tetracycles, 258 retained nearly two-thirds of the activity of artemisinin. The Fe(II)-induced rearrangement product 281, a quite stable epoxide was submitted for antimalarial assay and found to be completely devoid of activity. As 258 is a potent antimalarial but the epoxide 281 is not, it seems reasonable to suggest that the antimalarial activity of 258 is unrelated to epoxy intermediates. 

Mol, M.A. (1999). Implications of protein alkylation and proteolysis on vesication caused by sulfur mustard. Pentagon Reports. TNO Prins Maurits Laboratorium, Rijswijk (Netherlands), 62 pp. 

Tilley, SD, Francis MB. Tyrosine-selective protein alkylation using pi-allylpalladium complexes. J. Am. Chem. Soc. 2006 128 1080-1081. 

Since in peptides and proteins alkyl halides at pH 2.8 react only with the sulfur of methionine (Gundlach et al, 1959b), this procedure permits specific chemical cleavage of methionyl peptide bonds. 

Boffa LC, Bolognesi C. 1986. In vitro DNA and nuclear proteins alkylation by 1,2-dimethylhydrazine. Mutat Res 173 157-162. 

A transition metal catalyst has also been used to effect the reductive alkylation of amino groups on proteins [41], This reaction uses [Cp Ir(4-4 -dimethoxybipy)(H20)]S04 31 as a mild transfer hydrogenation catalyst and formate ion as the stoichiometric hydride source, in Fig. 10.3-11 (a). Presumably, this reaction occurs via the reversible formation of imine 33 with free amino groups on the protein surface, followed by reduction of iridium hydride 32. For most proteins, multiple modifications are observed (Fig. 10.3-ll(b)), although the overall level of conversion can be altered through variation of either the reaction temperature or the concentrations of the aldehyde and catalyst. In general, the reaction has shown excellent reliability for protein alkylation between pH 5 and 7.4. 

He, K., Y.A. He, G. Szklarz, J.R. Halpert, and M.A. Correia (1996). Secobarbital-mediated inactivation of cytochrome P450 2B1 and its active site mutants Partitioning between heme and protein alkylation and epoxidation. J. Biol. Chem. 271, 25864-25872. 

Mechanism. Numerous studies on the mechanism of IPO toxicity have supported the view that tissue damage by the compound is due to a highly reactive, alkylating metabolite(s) (Figure 2)(12). In vitro experiments demonstrated that this metabolic activation is catalyzed by a cytochrome P-450 enzyme system which is located in the endoplasmic reticulum of target cells(lO). This metaboliteCs) forms covalent bonds with cellular macromolecules, and it causes cell death (necrosis). The amount of cellular necrosis (measured by microscopic examination of the respective tissues 24 hours after exposure to the toxin) and the extent of protein alkylation (assayed by employing or H-IPO and measuring the amount of label... 

Talbot, B. Desnoyers, S. Castonguay, A. Immunoassays for proteins alkylated by nicotine-derived N-nitrosamines. Arch. Toxicol., 64 3 -4. 1990. 

For compounds with medium s such as ethyl, propyl, and butyl methane-sulfonates (5 = 0.67 —0.68), but not for the isopropyl ester, the mutation curve in barley as well as that in E, coli starts to rise at some dose above 0.2-LD5O. Very high mutation frequencies are reached around LD50 cf. Ehrenberg a/., 1966 Turtoczky and Ehrenberg, 1969). The mechanism involved in this avalanche is still unclear. The pattern of DNA alkylations or simultaneous protein alkylation, together with secondary changes in the DNA that are characteristic of the introduced alkyl, may be involved. 

Relative growth based on untreated casein as 100% Total AAA-total /imoles of alkylatable amino acids (lysine, histidine, methionine, and cysteine) per 100 gm of diet Dietary proteins at 1.0% protein alkylated with 3.5 mM chlorogenic acid/kg diet wwt. 

Increased expression of anti-apoptotic proteins, Alkylating agents, CoLE and Tannock... 

ReAL reagents, 4-bromomethyl-3-nitrobenzene and derivatives were synthesized. These compounds, upon binding to the protein, alkylate via the reactive bromomethyl group at a nucleophilic site. 

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