We determined the binding kinetics of seven tachykinins targeting the NK1 receptor. Dissociation rate constants (koff) ranged from 0.026 ± 0.0029 min−1 (Sar9,Met(O2)11-SP) to 0.21 ± 0.015 min−1 (septide). Association rate constants (kon) were more diverse: substance P (SP) associated the fastest with a kon value of 0.24 ± 0.046 nM−1 min−1 while neurokinin A (NKA) had the slowest association rate constant of 0.001 ± 0.0002 nM−1 min−1. Kinetic binding parameters were highly correlated with potency and maximal response values determined in label-free impedance-based experiments on U-251 MG cells.
Our research demonstrates large variations in binding kinetics of tachykinins which correlate to receptor activation. These findings provide new insights into the ligand–receptor interactions of tachykinins and underline the importance of measuring binding kinetics of both drug candidates and competing endogenous ligands.