Comparative study on thermal denaturation modes of myosin in walleye pollack and carp myofibrils as affected by salt concentration

Abstract

The effect of salt concentration on the thermal denaturation profile of myosin in walleye pollack and carp myofibrils was compared by studying the subfragment-1 (S-1) and rod denaturation rates upon heating. Species-specific denaturation mode observed at 0.1 M KCl was no longer detected when samples were heated above 0.5 M KCl, where S-1 and rod denaturation rates were identical to each other. As the heating of the chymotryptic digest of myofibril formed practically no rod aggregates, S-1 denaturation in a form of myosin was the rate limiting step for rod aggregate formation. As the aggregate formation by rod was remarkably suppressed by lowering the temperature, the free movement of myosin tail upon heating was suggested to play an important role in the rod aggregate formation in a high salt medium.

Myosin denaturation in heated myofibrils of scallop adductor muscle

“…Ca 2+ -ATPase inactivation was well explained by the decrease of amount of S-1 reasonably because ATPase active site locates in the part, which was the same conclusion as obtained with fish myofibrils [9]. Loss of salt solubility and monomeric myosin content was well explained by the rod denaturation.…”

“…1 A fast rod denaturation relative to S-1 was characteristic for scallop myofibrils heated at 0.1 M KCl. We reported that relatively large magnitude of stabilization by F-actin leads to a fast rod denaturation with fish species [9]. A rapid denaturation of rod observed with scallop myofibrils can be explained similarly with a great stabilization extent.…”

“…Myosin denaturation upon heating of myofibrils was studied by monitoring the following changes; Ca 2+ -ATPase activity, salt solubility, monomeric myosin content, and the amount of S-1 and rod produced and their monomeric form as previously reported [9]. Chymotryptic digestion was performed for 60 min at 20°C in a digestion medium of 0.1 M KCl, 20 mM Tris-maleate (pH 7.0) and 1 mM EDTA using 1/400 (w/w) of chymotrypsin over myofibrils.…”

“…Dilution method rather than dialysis method was chosen for the easier procedures. Salt-soluble myosin content, monomeric myosin content, and the amount of chymotryptic S-1 and rod together with their monomeric form were all measured as reported earlier [9]. Contents were calculated by using SDS-PAGE and staining intensity measurement of the corresponding bands as described before [7].…”

Thermal denaturation profiles of catfish and tilapia myofibrils as affected by pH for heating

“…The magnitude calculated with catfish was about 100 times, which was the same as tilapia and was much greater than those calculated with carp and Alaska pollock myofibrils showing only 10 to 30 times [18].…”