Figure 3.

Organization of the A-band in natively isolated myofibrils shows that myosin heads can adopt two interactions with thin filaments

(A) XY-slices through a tomogram at three different Z positions (illustrated by the cartoon below), highlighting the myosin head densities (orange, yellow, and magenta) and the thin filament (green) apparent within the volume. Annotation of densities produces a volume in which filtered actomyosin can be fitted, shown on the right and in (B). The three myosin colors represent the contribution of the myosin head from a respective neighboring thick filament. Scale bars, 20 nm.

(B) Fitted model of all thin filaments and myosin heads in a tomogram, with the black inset depicting the filament shown in (A) In the XZ view, reconstructions of corresponding thick filaments are also shown.

(C) A typical cross-bridge with a myosin double-head.

(D) A rare myosin split-head with two heads from the same myosin molecule binding to two different actin filaments.

See also Figures S2 and S4 and Video S1.