Thermal transitions of actin

• Published in: Journal of thermal analysis and calorimetry Vol. 95; no. 3; pp. 713 - 719
• Main Authors: LORINCZY, D, VERTES, Zsuzsanna, KÖNCZÖL, Franciska, BELAGYI, J
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Dordrecht Springer Netherlands 01.03.2009; Springer
• Subjects: Analytical Chemistry; Analytical, structural and metabolic biochemistry; Biochemical and Pharmaceutical Aspects; Biological and medical sciences; Chemistry; Chemistry and Materials Science; Contractile proteins; Fundamental and applied biological sciences. Psychology; Holoproteins; Inorganic Chemistry; Measurement Science and Instrumentation; Physical Chemistry; Polymer Sciences; Proteins; myosin; F-actin; G-actin; DSC; EPR; thermal unfolding; Differential scanning calorimetry; Thermal transition; Conformational dynamics; Denaturation; EPR spectrometry; Unfolding; Contractile protein; Conformational changes; Actin; Myosin; Thermal analysis
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-008-9406-3

Actin is one of the main components in the eukaryote cells which plays significant role in many cellular processes, like force-generation, maintenance of the shape of cells, cell-division cycle and transport processes. In this study the thermal transitions of monomer and polymerized actins were studied to get information about the changes induced by polymerization and binding of myosin to actin using DSC and EPR techniques. The main thermal transition of F-actin was at 67.5°C by EPR using spin-labeled actin (the relative viscosity change was around 62°C), while the DSC denaturation T m s were at 60.3d°C for G-actin and at 70.5°C for F-actin. Applying the Lumry-Eyring model to obtain the parameters of the kinetic process and calculate the activation energy, a ‘break’ was found for F-actin in the function of first-order kinetic constant vs . 1/ T . This indicates that an altered interdomain interaction is present in F-actin. The addition of myosin or heavy meromyosin (HMM) in different molar ratio of myosin to actin has changed significantly the EPR spectrum of spin-labeled F-actin, indicating the presence of the supramolecular complex. Analyzing the DSC traces of the actomyosin complex it was possible to identify the different structural domains of myosin and actin.