Interaction of F-actin with phosphate analogues studied by differential scanning calorimetry.

The thermal unfolding of F-actin and the changes induced in it by the binding of phosphate analogues were studied by differential scanning calorimetry. It is shown that the conformation of actin is drastically altered by interaction with beryllium fluoride or aluminium fluoride, while the effects of vanadate and phosphate are negligible. The effect of beryllium fluoride on the F-actin structure, as reflected in a significant increase of the actin thermal stability, is much more pronounced in the presence of Mg2+ than in the case of F-actin polymerized by KCl or LiCl in the absence of Mg2+. It is concluded that differential scanning calorimetry is a very convenient method for probing the conformational changes in F-actin caused by the interaction with phosphate analogues.