Arginine modification

Arginine residues are very resistant to most of the usual reagents used for chemical modification. King (166) has reported the conversion of these residues to S-N- (2-pyrimidinyl) ornithine by treatment with malonaldehyde in 10 N HC1. Essentially complete modification of the 4 arginine residues in RNase was obtained. Peptide bond cleavage and disulfide interchange also occurred, however, and no conclusions are warranted on the relation of the properties of the product to the actual arginine modification. 

Smith BC, Denu JM (2009) Chemical mechanisms of histone lysine and arginine modifications. Biochim Biophys Acta 1789 45-57... 

M. A. Glomb and G. Lang, Isolation and characterization of glyoxal-arginine modifications, J. Agric. Food Chem., 2001, 49, 1493-1501. 

Histone methylation is a common posttranslational modification fond in histones. Histone methylations have been identified on lysine and arginine residues. In case of lysines S-adenosyl-methionine (SAM) dependent methyl transferases catalyze the transfer of one, two or three methyl groups. Lysine methylation is reversible and lysine specific demethylases have been... 

Neurotoxins present in sea snake venoms are summarized. All sea snake venoms are extremely toxic, with low LD5Q values. Most sea snake neurotoxins consist of only 60-62 amino acid residues with 4 disulOde bonds, while some consist of 70 amino acids with 5 disulfide bonds. The origin of toxicity is due to the attachment of 2 neurotoxin molecules to 2 a subunits of an acetylcholine receptor that is composed of a2 6 subunits. The complete structure of several of the sea snake neurotoxins have been worked out. Through chemical modification studies the invariant tryptophan and tyrosine residues of post-synaptic neurotoxins were shown to be of a critical nature to the toxicity function of the molecule. Lysine and arginine are also believed to be important. Other marine vertebrate venoms are not well known. 

SUGANO M, ISHIWAKI N, NAKASHIMA K (1984) Dietary protein-dependent modification of serum cholesterol level in rats significance of Arginine/lysine ratio. rinw Nutr Metab, 28 192-9. 

Formaldehyde reacts with proteins to form adducts and cross-links.31516 Metz et al.3 have identified three types of chemical modifications after treatment of proteins with formaldehyde (a) methylol (hydroxymethyl) adducts, (b) Schiff bases, and (c) methylene bridges. The reaction of formaldehyde with proteins is summarized in Figure 19.1, but briefly, formaldehyde reacts primarily with lysine and cysteine to form methylol adducts. The methylol adduct can subsequently undergo a dehydration reaction to form a Schiff base. Adducted primary amine and thiol groups can undergo a second reaction with arginine,... 

Many recent studies have focused on the mechanisms of formaldehyde modification, cross-linking, and reversal.19,37 8 In general, these studies found that formaldehyde is very specific, particularly when reaction times are relatively short. The amino-termini, lysine, tryptophan, and cysteine are the targets of modification in this case. Longer reaction times reveal more extensive modifications, including arginine, histidine, tyrosine, and phenylalanine. 

The most significant amino acids for modification and conjugation purposes are the ones containing ionizable side chains aspartic acid, glutamic acid, lysine, arginine, cysteine, histidine, and tyrosine (Figure 1.6). In their unprotonated state, each of these side chains can be potent nucleophiles to engage in addition reactions (see the discussion on nucleophilicity below). 

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