Chemical Bypass of General Base Catalysis in Hedgehog Protein Cholesterolysis Using a Hyper-Nucleophilic Substrate.

ABSTRACT: Proteins in the hedgehog family undergo self-catalyzed endoproteolysis involving nucleophilic attack by a molecule of cholesterol. Recently, a conserved aspartate residue (D303, or D46) of hedgehog was identified as the general base that activates cholesterol during this unusual autoprocessing event; mutation of the catalyzing functional group (D303A) reduces activity by >104-fold. Here we report near total rescue of this ostensibly dead general base mutant by a synthetic substrate, 3?-hydroperoxycholestane (3HPC) in which the sterol -OH group is replaced by the hyper nucleophilic -OOH group. Other hedgehog point mutants at D303, also unreactive with cholesterol, accepted 3HPC as a substrate with the rank order: WT > D303A ? D303N ? D303R, D303E. We attribute the revived activity with 3-HPC to the ?-effect, where tandem electronegative atoms exhibit exceptionally high nucleophilicity despite relatively low basicity.

SUBMITTER: Ciulla DA 

PROVIDER: S-EPMC6054137 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature