JBC, Vol. 252, Issue 10, 3374-3378, May, 1977
Interaction between Acanthamoeba actin and rabbit skeletal muscle tropomyosin
Y. Z. Yang, D. J. Gordon, E. D. Korn and E. Eisenberg
The binding of 125I-labeled muscle tropomyosin to Acanthamoeba and muscle
actin was studied by ultracentrifugation and by the effect of tropomyosin
on the actin-activated muscle heavy meromyosin ATPase activity. Binding of
muscle tropomyosin to Acanthamoeba actin was much weaker than its binding
to muscle actin. For example, at 5 mM MgCl2, 2 mM ATP, and 5 micronM actin,
tropomyosin bound strongly to muscle actin but not detectably to
Acanthamoeba actin. When the concentration of actin was raised from 5
micronM to 24 micronM in the presence of 80 mM KCl, the binding of
tropomyosin to Acanthamoeba actin approached its binding to muscle actin.
As with muscle actin, the addition of muscle heavy meromyosin in the
absence of ATP induced binding of tropomyosin in Acanthamoeba actin under
conditions were binding would otherwise not have occurred. The most
striking difference between the interactions of muscle tropomyosin with the
two actins, however, was that under conditions where tropomyosin was found
to both actins, its stimulated the Acanthamoeba actin-activated heavy
meromyosin ATPase but inhibited the muscle actin-activated heavy meromyosin
ATPase.
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