Figure 5.

The amounts of the 38k protein coprecipitated by binding to myosin and its fragments, and striated muscle myosins. The assembly of unphosphorylated myosins was observed only in the presence of the 38k protein (see Fig. 3). The assembly of rod, LMM, skeletal, and cardiac myosins do not require the 38k protein. About 95% of total amount of rod, 85% of that of LMM, 90% of that of skeletal and cardiac myosins could be precipitatable under our assay conditions. The 38k protein was mixed with 1.1 μM of various types of myosin and its fragments and centrifuged to coprecipitate with them. The amounts of the 38k protein recovered in the precipitate were quantified by the densitometry. Rod (open circles), LMM (closed circles), unphosphorylated myosin (open triangles), skeletal (open squares), and cardiac myosins (closed squares). Data are from the average of two sets of independent experiments. Inset, Gel filtration pattern of the mixture of HMM and the 38k protein. The mixture of 8.5 μM HMM and 40 μM 38k protein in 300 μl buffer A was applied to Superose 6 equilibrated with buffer A and eluted with buffer A in a flow rate of 0.5 ml/min. A₂₈₀ in arbitrary unit (ordinate) was plotted against elution time (abscissa). HMM and the 38k protein was separately eluted in the peak at 31 and 35 min, respectively. SDS-PAGE patterns of peak fractions of HMM (left) and the 38k protein (right) were also shown. Arrowheads indicate HMM (H) and the 38k protein (38).