Mulligan, Christopher, Mindell, Joseph A (2013) Mechanism of transport modulation by an extracellular loop in an archaeal excitatory amino acid transporter (EAAT) homolog. Journal of Biological Chemistry, 288 (49). pp. 35266-35276. ISSN 1083-351X. (doi:10.1074/jbc.M113.508408) (KAR id:61671)
PDF
Author's Accepted Manuscript
Language: English |
|
Download this file (PDF/1MB) |
|
Request a format suitable for use with assistive technology e.g. a screenreader | |
Official URL: http://dx.doi.org/10.1074/jbc.M113.508408 |
Abstract
Secondary transporters in the excitatory amino acid transporter family terminate glutamatergic synaptic transmission by catalyzing Na(+)-dependent removal of glutamate from the synaptic cleft. Recent structural studies of the aspartate-specific archaeal homolog, Glt(Ph), suggest that transport is achieved by a rigid body, piston-like movement of the transport domain, which houses the substrate-binding site, between the extracellular and cytoplasmic sides of the membrane. This transport domain is connected to an immobile scaffold by three loops, one of which, the 3-4 loop (3L4), undergoes substrate-sensitive conformational change. Proteolytic cleavage of the 3L4 was found to abolish transport activity indicating an essential function for this loop in the transport mechanism. Here, we demonstrate that despite the presence of fully cleaved 3L4, Glt(Ph) is still able to sample conformations relevant for transport. Optimized reconstitution conditions reveal that fully cleaved Glt(Ph) retains some transport activity. Analysis of the kinetics and temperature dependence of transport accompanied by direct measurements of substrate binding reveal that this decreased transport activity is not due to alteration of the substrate binding characteristics but is caused by the significantly reduced turnover rate. By measuring solute counterflow activity and cross-link formation rates, we demonstrate that cleaving 3L4 severely and specifically compromises one or more steps contributing to the movement of the substrate-loaded transport domain between the outward- and inward-facing conformational states, sparing the equivalent step(s) during the movement of the empty transport domain. These results reveal a hitherto unknown role for the 3L4 in modulating an essential step in the transport process.
Item Type: | Article |
---|---|
DOI/Identification number: | 10.1074/jbc.M113.508408 |
Uncontrolled keywords: | Amino Acid Transport, Chemical Modification, Glutamate, Membrane Transport, Reconstitution of Membrane Transporters, Transporters, Protein Cross-linking |
Subjects: |
Q Science > Q Science (General) Q Science > QP Physiology (Living systems) > QP517 Biochemistry |
Divisions: | Divisions > Division of Natural Sciences > Biosciences |
Depositing User: | Christopher Mulligan |
Date Deposited: | 10 May 2017 13:51 UTC |
Last Modified: | 16 Nov 2021 10:24 UTC |
Resource URI: | https://kar.kent.ac.uk/id/eprint/61671 (The current URI for this page, for reference purposes) |
- Link to SensusAccess
- Export to:
- RefWorks
- EPrints3 XML
- BibTeX
- CSV
- Depositors only (login required):