NMIIA is enriched in protrusions and active NMIIB localizes to dorsal perinuclear fibers. MDA-MB 231 cells fixed and immunostained 1 h after plating for NMIIA and NMIIB (A), NMIIA and pMLC (B), or NMIIB and pMLC (C). (D, i) MDA-MB 231 cells fixed and stained for NMIIA and NMIIB 16 h after plating. Dashed box indicates field for ii and iii. NMIIA is enriched in protrusions and NMIIB is enriched in lateral stress fibers (arrows). (D, ii) NMIIA forms basal perinuclear stress fibers. (D, iii) Dorsal localization of NMIIA and NMIIB. (E, i) MDA-MB 231 cell fixed and stained for NMIIB and pMLC 16 h after plating. Dashed box indicates field for ii and iii. NMIIB colocalizes with pMLC in basal perinuclear stress fibers (ii) and in dorsal stress fibers (iii, arrowheads). Bars, 10 µm.