Gated ion transporters

Motomov, M., Tam, T. K., Pita, M., Tokarev, L, Katz, E., Minko, S. (2(X)9). Switchable selectivity for gating ion transport with mixed polyelectrolyte brushes approaching smart drug delivery systems. Narwtechrwlogy, 20,434006. 

Artificial ion channels advantages, 38-39 design of gated ion transporters,... 

Neurotransmitter transport can be electrogenic if it results in the net translocation of electrical charge (e.g. if more cations than anions are transferred into the cell interior). Moreover, some transporters may direction-ally conduct ions in a manner akin to ligand-gated ion channels this ion flux is not coupled to substrate transport and requires a separate permeation pathway associated with the transporter molecule. In the case of the monoamine transporters (DAT, NET, SERT) the sodium current triggered by amphetamine, a monoamine and psychostimulant (see Fig. 4) is considered responsible for a high internal sodium concentration... 

Synaptic Transmission. Figure 1 Synaptic transmission. The presynaptic terminal contains voltage-dependent Na Superscript and Ca2+ channels, vesicles with a vesicular neurotransmitter transporter VNT, a plasmalemmal neurotransmitter transporter PNT, and a presynaptic G protein-coupled receptor GPCR with its G protein and its effector E the inset also shows the vesicular H+ pump. The postsynaptic cell contains two ligand-gated ion channels LGIC, one for Na+ and K+ and one for Cl-, a postsynaptic GPRC, and a PNT. In this synapse, released transmitter is inactivated by uptake into cells. 

Figure 2. Carrier (a) and channel (b) mechanisms for facilitated ion transport across the membrane. Carrier encapsulates ion and moves across the membrane and releases the ion at the other end. It shuttles in the membrane as a carrier-metal complex. Channel is, in principle, an aqueous pore structured in the membrane. Ion can traverse through the membrane more or less freely in the pore with recognition at the selectivity filter when the gate is open. Here illustrated is a voltage sensitive gate as an example. ...

FIGURE 8. Current model for the gating mechanism in the CorA transporter. Left closed conformation with the magnesium binding sites in the sensor occupied. Right postulated open conformation allowing ion transport into the ceU. Adapted by permission of MacmiUan Publishers Ltd. from Reference 71... 

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