It is generally agreed that constraints on the curvature and flexibility of tropomyosin are necessary both for the binding and regulatory movements of tropomyosin on actin filaments. It follows that mutagenesis of residues that may affect curvature and/or flexibility is commonly used as an analytical tool. The tropomyosin coiled-coil is stabilized by hydrophobic residues in the "a" and "d" positions of its heptad repeat. However, a highly conserved Asp137 places a negative charge on each chain in a position typically occupied by hydrophobic residues. Substituting a canonical Leu for Asp137 suggested that Asp137 destabilizes tropomyosin and imparts flexibility (Sumida et al., 2008). The D137L mutant does retain F-actin binding properties. We have now assessed changes of curvature and flexibility by EM and Molecular Dynamics (MD) on the Leu137 mutant. Contrary to expectation, rotary shadowed D137L tropomyosin is more curved, not straighter, than control tropomyosin. Moreover, overall the average MD shape of the molecule is extremely bent and, unlike wild type tropomyosin, does not match the contours of the F-actin helix at all. We find that the persistence length of D137L is half that of wild-type tropomyosin (measured either on EM images or on MD frames), indicating that the mutant is more curved and more flexible than the wild type is. MD shows that there is a modest decrease in curvature in the surrounds of residue 137 in the D137L mutant, but it is accompanied by a large unexpected increase in curvature near residue 175. Thus we find that mutation at one site on tropomyosin leads to an unexpected delocalized change at another site along the molecule.