Figure 1.

Assessing A-ring specificity in HhC catalysis. (A) Hedgehog cholesterolysis. Precursor hedgehog undergoes peptide bond rearrangement at a conserved Gly-Cys motif; the resulting thioester is cleaved by substrate sterol (bracket), releasing HhN-sterol and HhC. Catalytic cysteine and aspartate acid residues of HhC depicted as ball-and-strick.(B) Sterols with variant A-ring structures assayed as alternative HhC substrates. Red circles, oxygen atom.