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Acta Physiologica 2011; Volume 202, Supplement 684
The Joint Conference (FAMÉ 2011) of the LXXVth Meeting of the Hungarian Physiological Society, XVIth Meeting of the Hungarian Society of Anatomists, Experimental Section of the Hungarian Society for Experimental and Clinical Pharmacology and Hungarian Society for Microcirculation and Vascular Biology
6/8/2011-6/11/2011
Pécs, Hungary
SKELETAL ACTIN DYNAMICS WITH DIFFERENT BOUND NUCLEOTIDES
Abstract number: P48
Konczol1 F., Turmer2 K., Belagyi2 J., Lorinczy2 D.
Aims:
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. It has been generally believed that the torsional flexibility of actin filaments and the amount of twisted structure correlate with the biological functions. Actin monomer, called G-actin, consists of four subdomains. The interaction between the subdomains is dynamic, as derived by several biophysical and structural studies; the subdomains might have different conformational and motional states depending on the bound cations and nucleotides, and on the interactions with small molecules and larger entities as proteins.
Methods:
In this work a spin label was attached to Cys-374 residue in F-actin, and the motional dynamics of the label was measured by EPR in both forms of actin when the bound ATP was exchanged by its non-hydrolyzable analogue AMP.PNP. Additional measurements carried out by DSC, in order to get thermodynamical data which correlate with the domain motions.
Results:
Temperature-dependent EPR measurements showed that the hyperfine splitting constant which reflects the rotational motion of the attached label in G-actin (AMP.PNP) increased in the whole temperature range in comparison with G-actin (ATP). Rotational correlation time of monomer actin increased from 18 ns up to 32 ns at room temperature after nucleotide exchange. Similar tendency was concluded in the case of F-actin as well.
Conclusion:
Analysis of DSC transitions in samples of AMP.PNP-G-actin and AMP.PNP-F-actin showed that the local conformational changes detected by EPR measurements are coupled with global motions and domain interactions measured by DSC. The data of both measurements showed significant increase in EPR and DSC parameters after nucleotide exchange (AMP.PNP-G-actin melting temperature Tm=65.2 °C, AMP.PNP-F-actin Tm=74.1 °C).
Support:
OTKA CO-123 (EPR, for J. B.) and CO-272 (DSC, for D. L.)
To cite this abstract, please use the following information:
Acta Physiologica 2011; Volume 202, Supplement 684 :P48