Dissociative mechanism of F-actin thermal denaturation.
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.
Mikhailova
V V
VV
Bach Institute of Biochemistry, Russian Academy of Sciences, 119071 Moscow, Russia.
Kurganov
B I
BI
Pivovarova
A V
AV
Levitsky
D I
DI
D008841:Actin Cytoskeleton / Q000737:chemistry / Q000187:drug effects; D000199:Actins / Q000737:chemistry*; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002152:Calorimetry, Differential Scanning; D011232:Chemical Precipitation; D006358:Hot Temperature; D008954:Models, Biological; D009994:Osmolar Concentration; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D011817:Rabbits
D000199:Actins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate