In contrast to the V360P substitution, the increased stability of the wide-open state observed for Chimera 2 can be rationalized by the S361E substitution, which enables Chimera 2 to form an intra-loop hydrogen bond with W354 and an inter-loop hydrogen bond with Q412 (Figure ). This is consistent with our RMSF calculation in that the central portion of the WPD-loop becomes notably more stable in Chimera 2 over Chimera 3 (Figures and).