221117 nanion 1026x196 03Research Ins]i[ghts: Nanion’s Transporter Webinar Series 2022

Join us over the course of a year as we dive into a series of 3 sessions (a collection of scientific presentations/talks; representing academia & industry alike) scheduled across 2022. Whether you join us from an academic or industry setting, we invite you to join us a cross the course of the year to dive deep into all things transporters. Our aim is to provide a unique platform for researchers globally to share their work and engage in meaningful active discussions. All talks will be live and accessible on-demand upon completion of the scheduled event.


17.11.2022 - Charge translocation reveals new insights into the transport mechanisms of human antiporters

Session Abstract: 

Ion exchangers antiport different ion species across the membrane, depending on their natural electrochemical gradients. They contribute to cellular ion homeostasis and provide substrates to organelles for further metabolization. In session three of our Transporter Webinar Series 2022, Edmund Kunji and Dirk. J. Slotboom will present their recent work in this field, including data for the ATP/ADP carrier ANT1 and the electroneutral Na+/H+ exchanger NHA2.

Speakers: 

Title: Dissecting the charge movements during adenine nucleotide exchange by the mitochondrial ADP/ATP carrier

Edmund R.S. Kunji
(Cambridge University, United Kingdom)

Abstract: 

The mitochondrial ADP/ATP carrier, also called adenine nucleotide translocase or translocator, imports ADP into the mitochondrial matrix, where it is converted to ATP, and exports the newly synthesized ATP to the cytosol, where it fuels the metabolic energy-requiring processes that are vital for cell survival. These carriers belong to the largest transport protein family in humans, called the SLC25 Mitochondrial Carrier Family. The cycle between a cytoplasmic-open state and matrix-open state during the transport of these substrates, both of which are structurally resolved. Comparison of the two states shows that the carrier has six dynamic elements for the state interconversions, which support an alternating access mechanism, consisting of three core elements and three gate elements. When the carrier changes from the cytoplasmic-open to the matrix-open state, the three gate elements move inwards, closing the cytoplasmic side of the carrier, whereas the three core elements move outwards, opening the matrix side. The converse occurs when the carrier changes from the matrix-open to the cytoplasmic-open state. The carrier functions as a monomer and has a single substrate binding site and two networks on either side of central cavity that open and close the carrier during the transport cycle in an alternating way. These structural and functional features are only compatible with a ping-pong kinetic mechanism, but this leaves a major bioenergetic challenge. How is ADP, which carries three negative charges, imported into mitochondria against the inside negative membrane potential? In this talk, we will dissect the molecular features of the carrier that contribute to the charge translocations during adenine nucleotide exchange, using the Nanion SURFE2R N1.


Title: Mechanistic insight in glutamate transport

Dirk J. Slotboom
(Groningen University, The Netherlands)

Abstract: 

Glutamate transporters of the SLC1 family are secondary active transporters that harness cation gradients across the plasma membrane as the driving force to pump the neurotransmitter L-glutamate from the synaptic cleft into neuronal and glial cells. The transporters are homotrimeric and operate via a so-called elevator mechanism, where the transport domain of each monomer can move trough the membrane to carry substrates from one side of the membrane to the other. In addition to pumping glutamate from the synaptic cleft, these transporters display a glutamate-gated chloride channel activity, which is thermodynamically uncoupled from glutamate transport. I will present structures of the prokaryotic glutamate transporter homologue GltTk embedded into lipid nanodiscs, determined by cryo electron microscopy. By titrating in substrate, we observed changes in the conformational ensemble, corresponding to turnover. We used SSM-based electrophysiology (by the Nanion SURFE2R N1) to measure the chloride conductance and show that a mutation at the homologous position as found in the human glutamate transporter EAAT1 of patients with episodic ataxia 6, causes increased chloride conductance relative to the amino acid transport rate. Together, these data provide insight in the transport mechanism.

 

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