Mechanism of Catch Force: Tethering of Thick and Thin Filaments by Twitchin

Figure 12

A belt and suspenders model of twitchin interaction with the thick and thin filaments in catch. The redundancy provided by two force-bearing tethers in each twitchin molecule is shown. The N- and C-terminal portions of twitchin that contain regulatory phosphorylation sites are shown to be independent tethers. The N-terminal tether shows the region surrounding the DX and D1 phosphorylation sites interacting with the thin filament, and the C-terminal tether shows the region surrounding the D2 phosphorylation site interacting with the thin filament. The evidence for the DXD1 region binding to the thin filament comes from this work and the evidence for D2 and adjacent Ig domains comes from [104, 105].