Figure 11. Structural rearrangement of the 7-stranded β-sheet.

(A) Side and top views of the central β-sheet are shown on the left- and right-hand side of the panel, respectively. Individual β-strands, β_i, are represented by red and black arrows indicating the direction of the rigor-like and NMSM post-rigor β-strand vectors, respectively. In the box diagrams, the twist of the entire sheet, τ, and the difference in the twist angle between the individual strands and β₇, Δτ_{i ,7}, relative to the rigor-like conformation are monitored along the NMSM path. The former is computed as , where and are the unit vectors corresponding to the structural borders of the β-sheet; the latter as Δτ_{i ,7}(ξ) = ∥τ_{i ,7}(ξ)−τ_{i ,7}(0)∥, where ξ = 0 indicates the rigor-like conformation and ξ = 1 the NMSM post-rigor conformation. (B) The comparison of the NMSM post-rigor conformation with the structure obtained by the pure rigid-body motion described by the screw axes given in Table 3; see text. The inset on the left shows the structural location of the central β-sheet in the myosin head.