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![[Figure 7]](hi3499fig7mag.jpg)
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Figure 7
(a) The structure of the actin myosin complex (Rayment, Holden et al., 1993  ; Schroeder et al., 1993). On the right-hand side are shown five actin molecules in an actin helix (Holmes et al., 1990), and on the left-hand side is shown a myosin cross bridge (S1) (Rayment, Rypniewski et al., 1993). 25 K fragment (green); 50 K upper fragment (red); 50 K lower fragment (white); the disordered chain between the 50 K domain and the 20 K domain (yellow loop – note this loop has been modelled); the first part of the 20 K domain including the SH2 helix (until 699) (light blue); the SH1 helix, converter domain and the C-terminal helix – `the neck' (dark blue); the regulatory light chain (magenta) and the essential light chain (yellow). Plates prepared using GRASP (Nicholls et al., 1991). This is the `end' state. (b) A reconstruction of the `beginning' state from the crystallographic data on the dictyostelium construct truncated at 761 and complexed with ADP.vanadate (Smith & Rayment, 1996). The missing `neck' or lever arm has been modelled from chicken S1 data. Note the 70° rotation of the lever arm. The rotation of the lever arm is controlled by the bending out of a helix (shown white) which contacts the γ-phosphate at its inner end (the so-called `switch-2' region). The distal end of the lever arm moves about 12 nm between the two states. |
![[Figure 7]](hi3499fig7.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
