Structural studies of selected signaling protein complexes.

The ability of proteins to bind other molecules in response to various stimuli in their microenvironment serves as a platform for extensive regulatory networks coordinating downstream cell actions. The correct function of these signaling pathways depends mostly on noncovalent interactions often affecting the structure of proteins and protein complexes. Understanding the molecular mechanism of a protein function in cell signaling therefore often depends on our knowledge of a three-dimensional structure. In this doctoral thesis, I present the work that led to the understanding of several protein-protein and protein-ligand interactions implicated in cell signaling at the molecular level. I applied nuclear magnetic resonance spectroscopy, small angle X-ray scattering and other biophysical methods to determine the molecular basis of inhibition of four signaling proteins: Calcium/Calmodulin (Ca2+ /CaM)-dependent protein kinase kinase 2 (CaMKK2); protease Caspase-2; Forkhead transcription factor FOXO3, and Apoptosis signal-regulating protein kinase 1 (ASK1). In particular, I investigated the distinct roles of 14-3-3 and Ca2+ /CaM in the regulation of CaMKK2 activity. I also studied in detail the mechanism how 14-3-3 interferes with the caspase-2 oligomerization and its nuclear localization as well as..