Molecular elasticity in the dimeric tail-to-tail myomesin My9--My13 filament.

The first part of the movie illustrates the overall architecture by zooming into and rotating the My9--My13 filament composite model and labeling the individual My domains (cf. Figure 1). The second part illustrates the collective effect that was observed in the AFM experiments (cf. Figure 6), mapped on the complete dimeric My9--My13 filament, allowing it to stretch by about 2.5 times its original length. The length estimates are indicated with a ruler. The extended model was built by straightening all Ig domains to one common orientation and by assuming unfolded helical linkers, as defined in Figures 2 and 3, with Cα--Cα spacings of 3.8 Å. The estimated length for all straightened My domain modules is 290 Å, and for unfolded helical linkers 570 Å, leading to an overall length of 860 Å, which is 2.5 times the length of the X-ray-based composite My9--M13 model, in the absence of external forces (340 Å). The color codes are as in Figure 1.

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