Key result
The thermal stability of F-actin strongly depends on ADP and protein concentration, with transition temperature increasing by almost 3 degrees C as F-actin concentration increases from 0.5 to 2.0 mg/ml.
Thermal denaturation of F-actin involves reversible stages including dissociation of ADP and subunits from filament ends, explaining its dependence on ADP and protein concentration.
We have applied differential scanning calorimetry to investigate thermal unfolding of F-actin. It has been shown that the thermal stability of F-actin strongly depends on ADP concentration. The transition temperature, T(m), increases with increasing ADP concentration up to 1 mM. The T(m) value also depends on the concentration of F-actin: it increases by almost 3 degrees C as the F-actin concentration is increased from 0.5 to 2.0 mg/ml. Similar dependence of the T(m) value on protein concentration was demonstrated for F-actin stabilized by phalloidin, whereas it was much less pronounced in the presence of AlF4(-). However, T(m) was independent of protein concentration in the case of monomeric G-actin. The results suggest that at least two reversible stages precede irreversible thermal denaturation of F-actin; one of them is dissociation of ADP from actin subunits, and another is dissociation of subunits from the ends of actin filaments. The model explains why unfolding of F-actin depends on both ADP and protein concentration.
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Mikhailova et al. (2006) studied this question. ADP and F-actin concentration was evaluated on Thermal stability (transition temperature, Tm). The thermal stability of F-actin strongly depends on ADP and protein concentration, with transition temperature increasing by almost 3 degrees C as F-actin concentration increases from 0.5 to 2.0 mg/ml.
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