Three dimensional models of isolated RPS4 proteins. The N and C termini are marked. (A) Structure of each RPS4 protein. β strands are in yellow, α helices in red and loops in green. (B) RPS4X showing the one residue that is different in the three RPS4 proteins (carbon atoms in cyan, oxygen atoms in red and nitrogen atoms in blue) and the residues that are different, with non-conservative substitutions, in one or both of the RPS4Y proteins (carbon atoms in grey, oxygen atoms in red and nitrogen atoms in blue). N-terminal domain is in green, central domain in yellow and C-terminal domain in cyan.