Microscopic kinetics and structure-function analysis in the vesicular acetylcholine transporter

The vesicular acetylcholine transporter (VAChT) resides in synaptic vesicles of cholinergic nerve terminals. It carries out vesicular storage of ACh. The amount of ACh stored determines, along with other factors, the amount of ACh released. Knowledge of the structure-function relationship in VAChT might enable pharmacological regulation of ACh storage and release at the level of VAChT. To this end, a quantitative model for the individual steps in the overall transport cycle of VAChT has been developed. Because of the particular values of the microscopic rate constants in the model, structure-function analysis of VAChT can be misleading. Attempts to devise a pro-storage strategy to increase ACh release from cholinergic nerve terminals should take into account the microscopic kinetics of this transporter.