Identification of cross-linking site(s) of myosin heavy chains in oxidatively stressed chicken myofibrils

The cross-linking site(s) of myosin heavy chains (MHC) in chicken myofibrils exposed to non-enzymatic, hydroxyl radical-generation oxidizing systems (HRGS) was investigated by means of chymotryptic digestion and subsequent electrophoresis. Oxidation of the chymotryptic digests resulted in cross-linking of the rod or light meromyosin (LMM) segment of MHC mostly via disulfide bonds, while subfragment-1 (S-1) or heavy meromyosin (HMM) was not affected. A mixture of cross-linked rod or LMM and uncross-linked S-1 or HMM was also produced when myofibrils were 1st oxidized and then digested with chymotrypsin, confirming that cross-linking of myosin in HRGS-oxidized myofibrils occurred initially in the LMM portion of the myosin rod.