Effect of ethanol on tropomyosin in solution and in reconstituted thin filaments.
The effects of ethanol at concentrations below 10% on the conformation of tropomyosin, its end-to-end polymerization, its binding to F-actin, and its effects on actomyosin ATPase activity were studied. Ethanol stabilized the tropomyosin conformation by shifting the helix thermal unfolding profile to higher temperatures, and increased the end-to-end polymerization of tropomyosin. Ethanol-induced changes in the excimer fluorescence of pyrene-tropomyosin indicated that its conformation was stabilized by ethanol both free and bound to F-actin. Effects of tropomyosin and tropomyosin-troponin on actomyosin ATPase activity were measured under conditions for which tropomyosin binding to F-actin increases the activity. Under conditions for which the binding of tropomyosin to F-actin is optimum, in the presence of tropomyosin, the actomyosin ATPase activity decreased as the ethanol concentration increased, further indicating that ethanol induces a structural change in the tropomyosin-F-actin complex. Under conditions for which the binding of tropomyosin to F-actin is weak (low salt or high temperature), addition of ethanol increased the ATPase activity due to increased binding of tropomyosin to F-actin. Thus, ethanol appears to modify actomyosin ATPase activity by increasing the binding of tropomyosin to F-actin and affecting the structure of tropomyosin in the tropomyosin-F-actin filament.
D000199:Actins; D000251:Adenosine Triphosphatases; D000818:Animals; D001704:Biopolymers; D055598:Chemical Phenomena; D002621:Chemistry; D000431:Ethanol; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D012996:Solutions; D013696:Temperature; D014335:Tropomyosin
D000199:Actins; D001704:Biopolymers; D012996:Solutions; D014335:Tropomyosin; D000431:Ethanol; D000251:Adenosine Triphosphatases