The tail domain of the myosin IIA and IIB heavy chain isoforms determines the subcellular localization, polarity phenotype, and exchange rate. (A) Cartoon depicting the domain swaps of MIIA and MIIB. Motor domains are represented in red, coiled-coil domains in blue. Unique sites used for PCR-based cloning are also shown. (B) Localization of MIIA, MIIB, and the two chimeras MIIA/B and MIIB/A. α-Actinin is used to locate the front and is shown in magenta in the colocalization panels; the myosin constructs are in green. Insets, detail of the localization of the myosin constructs in protruding areas. Note the absence of MIIB and MIIA/B in protrusions. Bar, 10 μm. (C and D) FRAP curves of MIIB/A (C) and MIIA/B (D). Average FRAP curves of wild-type MIIA and MIIB are also shown for comparison. Data are the mean ± SE of 24 individual measurements per condition in four independent experiments.