An acylated N-terminus and a conserved loop regulate the activity of the ABHD17 de-acylase

The dynamic addition and removal of long chain fatty acids modulates protein function and localization. The alpha/beta hydrolase domain-containing (ABHD) 17 enzymes remove acyl chains from membrane localized proteins such as the oncoprotein NRas, but how the ABHD17 proteins are regulated is unknown. Here, we used cell-based studies and molecular dynamics simulations to show that ABHD17 activity is controlled by two mobile elements - an S-acylated N-terminal helix and a loop - that flank the substrate-binding pocket. S-acylation at multiple sites buries the helix in the membrane, which allows hydrophobic residues in the loop to interact with the bilayer. This stabilizes the conformation of both helix and loop, alters the conformation of the binding pocket and optimally positions the enzyme for substrate engagement. S-acylation may be a general feature of acyl-protein thioesterases. By providing a mechanistic understanding of how the lipid modification of a lipid-removing enzyme promotes its enzymatic activity, this work contributes to our understanding of cellular S-acylation cycles.