Arginine residues chemical modification

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. 

Konishi, K., and Fujioka, M. (1987) Chemical modification of a functional arginine residue of rat liver glycine methyltransferase. Biochemistry 26, 8496-8502. 

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. 

The chemical modifications of cysteine sulfhydryl, histidine imidazole and arginine residues in lactate dehydrogenase lead to a total loss of enzymatic... 

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