Denaturation of Myosin and Its Subfragments
II. Effect of Thermal Treatment on Light Meromyosins
1972 年 71 巻 4 号 p. 661-673
詳細
1972 年 71 巻 4 号 p. 661-673
A new form of light meromyosin was prepared according to the method described by Young et al. (1). Thermostability of this protein (which they called LMM-C) was studied in comparison with tryptic light meromyosin fraction 1 (LMM Fr 1). Differences between LMM Fr 1 and LMM-C upon heating can be detected by solu-bility, viscosity, optical dispersion, difference spectrum (at U. V. region) and mor-phological studies. Upon thermal treatment, LMM Fr 1 depolymerizes to relatively low molecular weight proteins and peptides. The existence of a “temperature opti-mum” (60°C being more effective than 70°C) can be clearly observed. LMM-C, on the other hand, does not depolymerize, suggesting that it is more stable than LMM Fr 1 at high temperatures (45-60°C) under our experimental conditions. Addition of trypsin-trypsin inhibitor complex during the course of preparation of LMM-C and myosin converts the properties of the proteins to those of tryptic LMNI Fr 1, as far as their thermostability is concerned. Our experiments reported here seem to give full support to the view that protomyosins are formed upon thermal treatment by proteolytic contaminations, if they are present. We have considered whether LMM-C might represent a more natural form of α-rope section of myosin.
