Fig. 2. Sonic hedgehog interacts with heparin through the Cardin-Weintraub sequence. (A) Elution profile of SHH:AP and AlaSHH:AP from a heparin-agarose column in a continuous salt gradient. SHH:AP and AlaSHH:AP content of each fraction was quantified by its alkaline phosphatase activity. Two peaks are evident for SHH:AP but only one for AlaSHH:AP. (B) Elution behavior of SHH:AP and three mutants. The molarity of peak ligand elution was calculated from curve fits to the plot of NaCl concentration as a function of fraction number. Data are the mean±s.e.m. of three separate experiments. SHH:AP and Arg+SHH:AP behave identically with peaks of elution at 
0.5 and 0.75 M NaCl. By contrast, AlaSHH:AP and GlnSHH:AP each display only a single peak of elution at 0.5 M.
