Fig. 3

p.Ala710Val mutation causes structural changes in regulatory segment of the kinase styk-domain. The alanine residue is located in the position 710 of a regulatory segment known as a GS region, an approximately 30 amino acids motif that resides within the kinase styk-domain, which has threonine residue accessible for phosphorylation in order to activate the catalytic domain. The fragment of structural superposition of the styk-domains of GUCY2d protein and the p.Ala710Val mutant variant are shown by orange and magenta, respectively. The structure of the styk-domain of the p.Ala710Val mutant variant was equilibrated in water during 30 ns molecular dynamics at 37° to show structural changes due to the mutation. Alanine (yellow) is replaced with valine (red) residue in the mutant variant p.Ala710Val. The GS region is shown by 2 helices, H1 and H2, connected by a short loop. The p.Ala710Val mutation changes overall conformation of the GS region and causes a partial loss of helical structure in the H1 helix affecting the threonine 709 phosphorylation