Proteomic profiling of oxidized cysteine and methionine residues by hydroxyl radicals in myosin of pork

- Oxidation of specific cysteine and methionine were detected and quantified.
- Methionine is more sensitive to oxidation than cysteine in myosin.
- More cysteine was oxidized to form disulfide in coiled tail than head of myosin.
- Only the methionine in coiled tail of myosin was oxidized to sulfoxide and sulfone.

In order to investigate the effects of hydroxyl radicals on the myosin of pork, with focus on reducible and non-reducible oxidation of specific cysteine and methionine residues, extracted myofibrillar protein from longissimus dorsi of pork was incubated with H2O2 for 24, 48 and 72 h, respectively. The thiol contents and crosslinking of myofibrillar protein were analyzed after oxidation of the protein. Moreover, cysteine (labeled with N-ethylmaleimide (NEM) and iodoacetamide (IAM) before and after reduction, respectively) and methionine oxidation were detected by LC/MS using label-free quantitation. The result revealed that cysteine at head of myosin tended to form sulfinic and sulfonic acid, while the cysteine at coiled tail of myosin easily generated disulfide under same condition. Furthermore, it was also revealed that the methionine at the coiled tail of myosin was more easily oxidized than that of the head.