Aim 4

To look at the phosphorylation site of ribosomal protein eS6 and its possible impact on its surrounding structures to find out the role of eS6 phosphorylation.

The investigation of structural changes induced by eS6 phosphorylation is the fourth aim of this thesis. eS6 is a eukaryote-specific protein of the 40S subunit. It undergoes phosphorylation in response to various stimuli, including serum deprivation/restimulation. Surprisingly, there are almost no works tackling the role of eS6 phosphorylation from a structural perspective. Since structural information on the eukaryotic ribosome from crystal structures and cryo-EM density maps have emerged in the last years, eS6 could be structurally characterized in yeast and recently also in mammalian ribosomes. However, the last residues of the C-terminus of eS6, including all five phosphorylatable serines, are missing in the available structures, and similarly the neighbouring expansion segments are not well resolved, such that the phosphorylation and its structural consequences are not characterized yet (Behrmann et al., 2015; Ben-Shem et al., 2011). This thesis aims to investigate the C-terminal region of eS6 and its surrounding.