Fig. 1. Sonic hedgehog contains a Cardin-Weintraub consensus sequence for heparin binding. (A) Alignment of vertebrate sonic hedgehog and Drosophila Hedgehog protein sequences. Identical amino acids are in yellow and the putative heparin-binding domain is in blue. Green highlights indicate two absolutely conserved basic amino acid positions. Pictured below the sequence alignment is the Cardin-Weintraub consensus sequence for heparin binding; B represents basic amino acids. Red asterisk identifies N50, an amino acid involved in binding to PTCH. (B) Sequences of mutant SHH:AP generated in these studies. (C) Molecular model of SHH demonstrating the Cardin-Weintraub sequence (blue), and N50 and S156 (red asterisks), two amino acids involved in binding to patched [adapted from Pepinsky (Pepinsky et al., 2000)].