C-state to B-state pivoting of tropomyosin. Transverse sections through superposed 7UTI C-state and 7UTL B-state thin filament models but only with the tropomyosin positions displayed for comparison (gold, C-state tropomyosin; magenta, B-state tropomyosin). Selected slab sections show where the inner B- and C-state α-helices coincide, while the complementary outer pairs splay apart. This pattern is shown over tropomyosin residues 66–72, 105–110, 148–153, 187–193, 231–237, and 262–268, as indicated.