Effects of the N-terminal dynamics on the conformational states of human dopamine transporter.

Dopamine transporter mediates the neurotransmitter dopamine homeostasis in a sodium-dependent manner. The transport process involves an alternating access of a substrate to the extracellular and intracellular spaces, which is associated with different conformational states of the transporter. However, the underlying mechanism of modulation of the state transition remains elusive. Here we present a computational simulation study of human dopamine transporter to explore its two end states (outward-facing open and inward-facing open) that have not been determined experimentally. We show that the full-length transporter may tend to adopt the inward-facing open state in its free state. The binding of an amphetamine may not trap the transporter in the outward-facing open state with increasing length of the N-terminal. Furthermore, we identify distinct patterns in the interaction networks between the N-terminal and the intracellular region that could stabilize the state of the transporter, independent of substrate binding and phosphorylation. Our results reveal the essential role of the N-terminal dynamics in modulating the functional states of the dopamine transporter, providing molecular insights into the coupling of conformational transition and substrate passage in neurotransmitter transporters. When the N-terminal interacts with the intracellular region in an open manner, hDAT exhibits an outward-open conformation; whereas when the N-terminal collapses in the cytosol or interacts with the intracellular region in a closed manner, hDAT displays an inward-open conformation. [Display omitted] • The flexible N-terminal could modulate the conformational states of human dopamine transporter • The N-terminal Phosphorylation could increase the inward-open states of human dopamine transporter. • The collapsed N-terminal results in an inward-open state of human dopamine transporter. • The human dopamine transporter may share the same substrate transport path as human serotonin transporter. [ABSTRACT FROM AUTHOR]