Figure 6. Tropomyosin twisting on actin during MD.

Plots show the cumulative twist angle deviation from an idealized tropomyosin superhelical model, generated as described previously (Lehman et al 2018). The twist behavior of wildtype tropomyosin on actin (upper green curve) is compared to the twist behavior of D137L tropomyosin on actin (lower blue curve). In the wildtype, note that over-twisting begins near to residue 137 and gradually declines over about 40 residues towards the tropomyosin C-terminus. Also note that periodic twist undulations, roughly 40 residues apart, reflect the presence of alanine clusters (Li et al 2010; Lehman et al 2018); panel A adapted from Lehman et al (2018)). In contrast, D137L mutant tropomyosin shows an absence of cumulative twisting and irregular alanine cluster based twisting undulations.