Search

The roles of 7 conserved ionic residues in the 12 putative transmembrane domains (TMDs) of vesicular acetylcholine transporter (VAChT) were investigated, and transport and ligand binding were characterized at different pH values using filter assays. The pH effects indicate that sites that must be unprotonated for transport and vesamicol binding remain unidentified.

Tests to determine whether transport-dependent changes in exposure of the acetylcholine(ACh) binding site can be detected based on the ability of external ACh to compete with [(super 3)H] vasamicol for binding is reported. It was found that a molecule of vesicular acetylcholine transporter (VAChT) not bound to vasamicol binds and transports a molecule of ACh in the presence of proton-motive force and trace [H](super 3) vasamicol.

The acetylcholine (ACh) binding site in the vesicular acetycholine transporter (VAChT) is analyzed. The results show that analysis of microscopic kinetics is required for the correct interpretation of mutational effects in VAChT, which are discussed in terms of the three-dimensional structures for other transporters in the major facilitator superfamily.