FIGURE 5.

AgG3z8 N4A is a loss-of-function mutant that retains wild-type net secondary structure. A, dose-response curves of the AChR clustering activity of neural agrin (AgG3z8), N4A mutant, and muscle agrin (AgG3z0) plotted as log of concentration versus clustering activity. The wild-type and mutant proteins were each incubated at concentrations indicated with C2C12 myotubes grown in fusion medium for 5 h. The cells were then stained with rhodamine-α-bungarotoxin. AChR clusters (pixel density/microscopic field) in cultures exposed to 0.5 μm AgG3z8 were normalized to 100%. Each data point represents mean ± S.E. (error bars) of results from four independent experiments. B, superimposition of CD spectra of AgG3z8 and the N4A mutant in TBS. The data represent the mean of results from four separate experiments, each with six scans, and the S.E. is shown at every 10 nm of the wavelength.