Figure 5. Structural and sequence analysis of MSH3.

A: Multiple sequence alignment of MSH3. Jalview created visualization [120] using the first 500 amino acids of the mouse B6 MSH3 (NP_034959.2). Conservation values and consensus sequence are based on alignment of S. cerevisiae Msh3p, E. coli MutS and 17 mammalian MSH3 homologs; values range from 0–9, where 0 is lowest and 9 is the highest. Protein interacting domains indicated pertain to those regions of the human MSH3 protein. This panel only shows an abbreviated set of the species of MSH3 sequence, the full set analysed is shown in Figure S5. B: MSH3 variant within β-turn. The T321I variant occurs within a Type I β-turn, as determined by specific backbone turn angles [117], [118] from the human MSH3 structure (3THW_B). Top left: hMSH3 tube diagram of Cα atoms of β-turn (blue), i+2 (T) residue (red) and additional three residues on N- and C-terminal ends (green). Bottom left table shows the β-turn propensity is relatively strong throughout MutS/MSH3 homologs, while the CBy variant (Isoleucine at i+2 position) is extremely disfavored (table bottom left) [69]. Right: Ball and stick diagram of contact sites of Asp (D) and Thr (T) residues in β-turn with residues 194 and 214 respectively. Line diagram of Thr (T) hydroxyl group contact with neighbouring Threonine residue at position 365. The absence of the Threonine hydroxyl group may be important to stabilizing the β-turn itself, and/or may change the conformation of the turn, potentially disrupting distant contacts important for proper protein folding. MSH3 visualizations created using PyMol (PyMOL Molecular Graphics System, Version 1.2r3pre, Schrödinger, LLC).