Chameleonic Efficiency Shapes Ligand Access and Binding at TRPA1's Membrane-Facing Site

Selective antagonists of transient receptor potential ankyrin 1 (TRPA1), a cation-selective ion channel, are promising therapeutics for neuropathic pain and asthma. High-resolution TRPA1 structures reveal lipid-facing transmembrane binding sites that require ligands to partition into membranes for access. However, the role of membrane adaptability remains unclear. We investigated GDC-0334, a potent TRPA1 antagonist, and three analogs in heterogeneous membranes using molecular dynamics simulations. We introduce chameleonic efficiency (CE), a novel metric quantifying a ligand's ability to adopt both extended-open conformations required for membrane entry and tunnel access and the bent binding conformation, while achieving high and balanced populations of these states. GDC-0334 showed superior CE, reflected in a favorable membrane partitioning profile, entropy-driven conformational transitions, and robust binding interactions. Binding/unbinding simulations revealed shared extended-open intermediate conformations critical for site access. Analog potency tracked closely with CE, underscoring membranes as pharmacologically active biophases and providing actionable design principles for ligands targeting lipid-facing transmembrane sites.