Abstract
To elucidate the role of S-1 and rod in the polymerization of myosin heavy chain through SS bonding upon heating of actomyosin, each myofibril of carp (with 100μg/ml leupeptin), flying fish and rabbit was digested by ∝-chymotrypsin to S-1 and rod followed by heating for 1h at temperatures ranging from 10 to 80°C with added Cu2+ 12μM for carp and 100μM for other samples to enhance the oxidation of SH groups. SDS-PAGE and the measurement of SH content and surface hydrophobicity were performed. Behaviors of S-1 and rod from 3 species in common were as follows.
With the rising of temperature above 30°C, polymer at the top of 3% gel through SS bonding gradually increased with the concomitant decrease in S-1 and actin with Cu2+, while less polymer was found without Cu2+. This polymer was confirmed to be composed of S-1 and less amount of actin by two-step SDS-PAGE. Rod dimer through SS bonding was found almost at any heating temperatures except at 50°C where the degradation of rod occurred strongly.
Surface hydrophobicity increased clearly from 30°C, followed by gradual increase above 50°C. This behavior coincided very well with the increasing behavior of RSH upon heating without Cu2+. Oxidation of TSH was promoted with added Cu2+ slightly up to 30°C and greatly above 30°C, while RSH did so only a little below 30°C, and then greatly above 40°C in flying fish and 50°C in rabbit.
It was, therefore, concluded that the polymer formation of HC upon heating of actomyosin was mainly due to the oxidation of SH groups in S-1, while the dimer formation of HC was due to the oxidation of SH groups in rod.
