Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 292, Issue 18, Pages 7372-7384Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M116.757153
Keywords
amino acid transport; conformational change; metal ion-protein interaction; molecular dynamics; neurotransmitter transport; transporter
Categories
Funding
- National Institutes of Health [DA023694, DA012408, U54GM087519, DA022413, DA17293]
- National Institute on Drug Abuse Intramural Research Program
- Dahlem Research School (DRS)/Marie Curie Post-Doctoral Postdoc International (POINT) Fellowship at Freie Universitat Berlin
- Lundbeck Foundation [R126-2012-12576] Funding Source: researchfish
Ask authors/readers for more resources
Neurotransmitter:sodium symporters (NSSs) terminate neurotransmission by the reuptake of released neurotransmitters. This active accumulation of substrate against its concentration gradient is driven by the transmembrane Na+ gradient and requires that the transporter traverses several conformational states. LeuT, a prokaryotic NSS homolog, has been crystallized in outward-open, outward-occluded, and inward-open states. Two crystal structures of another prokaryotic NSS homolog, the multihydrophobic amino acid transporter (MhsT) from Bacillus halodurans, have been resolved in novel inward-occluded states, with the extracellular vestibule closed and the intracellular portion of transmembrane segment 5 (TM5i) in either an unwound or a helical conformation. We have investigated the potential involvement of TM5i in binding and unbinding of Na2, i.e. the Na+ bound in the Na2 site, by carrying out comparative molecular dynamics simulations of the models derived from the two MhsT structures. We find that the helical TM5i conformation is associated with a higher propensity for Na2 release, which leads to the repositioning of the N terminus and transition to an inward-open state. By using comparative interaction network analysis, we also identify allosteric pathways connecting TM5i and the Na2 binding site to the extracellular and intracellular regions. Based on our combined computational and mutagenesis studies of MhsT and LeuT, we propose that TM5i plays a key role in Na2 binding and release associated with the conformational transition toward the inward-open state, a role that is likely to be shared across the NSS family.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available