Conformational Propensities of Peptides Mimicking Transmembrane Helix 5 and Motif C in Wild-Type and Mutant Vesicular Acetylcholine Transporters

Chandrasekaran et al. (2006) J. Neurochem. 1, 1551−1559.]. In the current study, the structure of Loop 4/5, TM 5, and motif C were taken from a three-dimensional homology model for human VAChT. The peptide was immersed in implicit membrane and energy-minimized, and molecular dynamics (MD) were simulated. Kinking and wobbling occur in otherwise helical peptide at the hinge residues L226 and V227. MD also were simulated for A228G single mutant and V227L−A228A double mutant peptides to investigate the structural roles of the A228G mutation and β-branching at V227. Mutant peptides exhibit increased wobbling at the hinge residues, but in the double mutant the increase is less. Because motif C participates in the interface that mediates hypothesized rocker-switch reorientation of the acetylcholine binding site during transport, dynamics in motif C might be an important contributor to transport rate.