The Sonic Hedgehog (SHH) morphogen pathway is fundamental for embryonic development and stem cell maintenance and is implicated in various cancers. A key step in signaling is transfer of a palmitate group to the SHH N terminus, catalyzed by the multi-pass transmembrane enzyme Hedgehog acyltransferase (HHAT). We present the high-resolution cryo-EM structure of HHAT bound to substrate analog palmityl-coenzyme A and a SHH-mimetic megabody, revealing a heme group bound to HHAT that is essential for HHAT function. A structure of HHAT bound to potent small-molecule inhibitor IMP-1575 revealed conformational changes in the active site that occlude substrate binding. Our multidisciplinary analysis provides a detailed view of the mechanism by which HHAT adapts the membrane environment to transfer an acyl chain across the endoplasmic reticulum membrane. This structure of a membrane-bound O-acyltransferase (MBOAT) superfamily member provides a blueprint for other protein-substrate MBOATs and a template for future drug discovery.
5025 - 5038.e10
Hedgehog acyl transferase, Sonic Hedgehog signaling, cryo-EM structure, drug, heme, integral membrane protein, membrane-bound O-acyltransferase, molecular dynamics simulations, palmitoyl co enzyme A, small molecule inhibitor, Acylation, Acyltransferases, Allosteric Regulation, Animals, COS Cells, Catalytic Domain, Chlorocebus aethiops, Cryoelectron Microscopy, Enzyme Inhibitors, HEK293 Cells, Hedgehog Proteins, Heme, Humans, Membrane Proteins, Molecular Dynamics Simulation, Palmitoyl Coenzyme A, Protein Conformation, Signal Transduction, Structure-Activity Relationship