Authors:Réka Dudás, Tünde Kupi, Andrea Vig, J. Orbán, and D. Lőrinczy
The effect of phalloidin on the thermal stability of skeletal actin filaments polymerized from ADP-binding monomers was investigated
with the method of differential scanning calorimetry. Phalloidin shifted the melting temperature of the ADP-F-actin from 59.1±1.0
to 80.0±1.2°C. The stabilizing effect of phalloidin propagated cooperatively along the filament. The cooperativity factor
according to the applied model was 1.07±0.11. With these measurements it was possible to demonstrate that the binding of phalloidin
has lower influence on the adjacent protomers in ADP- (k=1) than in ATP-actin filaments (k=3).
Authors:Andrea Vig, Réka Dudás, Tünde Kupi, J. Orbán, G. Hild, D. Lőrinczy, and M. Nyitrai
The effect of phalloidin on filaments polymerized from ADP-actin monomers of the heart muscle was investigated with differential
scanning calorimetry. Heart muscle contains α-skeletal and α-cardiac actin isoforms. In the absence of phalloidin the melting
temperature was 55°C for the α-cardiac actin isoform and 58°C for the α-skeletal one when the filaments were generated from
ADP-actin monomers. After the binding of phalloidin the melting temperature was isoform independent (85.5°C). We concluded
that phalloidin stabilized the actin filaments of α-skeletal and α-cardiac actin isoforms to the same extent when they were
polymerized from ADP-actin monomers.