Oxidative Modifications of Protein Structures

Proteins, due to the complexity of their chemical structures, undergo oxidative modifications in subsequent stages which depend both on the presence of oxidation-susceptible groups and on steric availability of these groups for oxidant attacks (S25). Some oxidative structural modifications produced in proteins are common in various oxidants. Some modifications, such as chlorinated and nitrated protein derivatives produced in reactions with hypochlorite, peroxynitrite, and nitric dioxide, are specific for the oxidants employed. Certain oxidative protein modifications, such as interchain or intrachain disulfide bond formation or thiolation, are reversible and may be reduced back to the protein native form when oxidative stress is over (Dl). Other changes, such as sulfone formation, chlorination, and nitration, are irreversible and effect protein denaturation and promote its subsequent degradation. 

The methionyl residues, except for those buried inside the hydrophobic cores of protein molecules, are exposed to oxidants. This may effect a preferential spontaneous oxidation of methionyl residues, occurring both in vitro and in vivo (S59) (Fig. 10). 

Examples of Site-Located Specificity in Oxidation of Thiol and Thiether Residues 

Protein Thiols susceptible for oxidation Biological effect References 

Growth horomone (human) Met s4 and meti79 Abolition of binding ability to hGH receptor (Nb2 rat lymphoma cells) (Tl) 

---