INSTITUTE OF PHYSIOLOGY CAS - Study of regulator of proteins involved in the modulation of G-protein signaling: RGS3 and phosducin.

Phosducin (Pdc), a highly conserved phosphoprotein, plays an important role in the regulation of G-protein signalling, transcriptional control, and modulation of blood pressure. Pdc is negatively regulated by phosphorylation followed by binding to the 14-3-3 protein.

Biophysical studies

Our data show that the phosphorylation of the N-terminal domain of Pdc at Ser-54 and Ser-73 affects the structure of the whole Pdc molecule. Complex formation with 14-3-3 reduces the flexibility of both the N- and C-terminal domains of phosphorylated Pdc, as determined by time-resolved tryptophan and dansyl fluorescence. Therefore, our data suggest that phosphorylated Pdc undergoes a conformational change when binding to 14-3-3. These changes involve the G_tbg binding surface within the N-terminal domain of Pdc, and thus could explain the inhibitory effect of 14-3-3 on Pdc function.

Inhibitory effect of 14-3-3 protein on RGS3 function

In 2010 we solved the crystal structure of the RGS domain of at 2.3 Å resolution. The data obtained from the resolution of the structure of the RGS domain suggest that the 14-3-3 protein-induced conformational change affects the region within the Ga-interacting portion of the RGS domain (Rezabkova et. al., 2010).
In 2011 we have used small angle x-ray scattering, hydrogen/deuterium exchange kinetics, and Förster resonance energy transfer measurements to determine the low-resolution solution structure of the 14-3-3ζ:RGS3 complex (Rezabkova et al., 2011).
Finally to gain insight into the role of 14-3-3 in the regulation of Pdc function we studied structural changes of Pdc induced by phosphorylation and 14-3-3 protein binding using time-resolved fluorescence spectroscopy (Rezabkova et al., 2012).


Ribbon representation of the Pdc:G_tbg complex structure (Rezabkova et al., 2012).	SAXS low-resolution structure of the 14-3-3:pRGS3 complex (Rezabkova et al., 2011).