Actin is the component of several biological systems and it plays important role in different biological processes, especially in cell motility. The actin-based motility is accompanied with ATP-consume, and the irreversible ATP hydrolysis is coupled with the polymerization of monomer actin into filamentous form. When an actin monomer is incorporated into a filament, the ATPase is activated, and thereby the polymer formation is promoted. The polymer formation and the ATP hydrolysis is associated with internal motions and significant changes of the conformation in reaction partners. In this article, the ATP nucleotide in monomer actin was exchanged by its non-hydrolyzable analogue adenylyl-imidodiphosphate (AMP.PNP), and using two biophysical methods, electron paramagnetic resonance spectroscopy (EPR) and differential scanning calorimetry (DSC), we studied the local and global changes in globular and fibrous actin following the nucleotide exchange. The paramagnetic probe molecule-a maleimide spin label-was attached to Cys-374 site of monomer actin, and its rotational mobility was derived at different temperature. In DSC measurements the transition temperatures of samples with different bound nucleotides were compared. From the measurements we could conclude, that the nucleotide exchange induces changes in the internal rigidity of the actin systems, AMP.PNP-actins showed longer rotational correlation time and increased thermal transition temperature.
- Conformations of actins
- Nucleotide exchange
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry