Investigation of the Dual Functions in Catalysis and Membrane Binding of a Flexible Loop in Acyl Protein Thioesterase 2 & Lysophospholipase-like 1

Indianapolis, IN

Palmitoylation, through S-acylation of cysteine residues, is the only reversible lipid-based post-translational modification. Palmitoylation and depalmitoylation cycles control the subcellular concentration of essential signaling, transport, and immune regulation proteins. The depalmitoylation of proteins at the plasma membrane is catalyzed by two homologous proteins known as acyl protein thioesterases. For this project, we studied the potential function of a flexible loop to control the membrane binding and catalytic activity of acyl protein thioesterase 2 (APT2) and a similar protein, identified as lysophospholipase-like 1 (LYPLA1A). Through a combination of exposed hydrophobic residues bracketed by cationic residues, this flexible loop has been hypothesized to control the membrane binding activity of APT2 and LYPLA1A to regulate their activity near the membrane surface. For this project, we assembled a small collection of LYPLA1A and APT2 wild-type proteins and analyzed the differential catalytic activity expressed between the two. Based on our combined analysis, wild-type LYPLA1A and APT2 both demonstrate unique substrate specificities that could point toward pertinent biological functions on the membrane. We are continuing to investigate how the different sections of the flexible loop may affect enzyme activity and membrane binding between variants.