Publication Date:
2007-08-11
Description:
Na+/H+ antiporters are central to cellular salt and pH homeostasis. The structure of Escherichia coli NhaA was recently determined, but its mechanisms of transport and pH regulation remain elusive. We performed molecular dynamics simulations of NhaA that, with existing experimental data, enabled us to propose an atomically detailed model of antiporter function. Three conserved aspartates are key to our proposed mechanism: Asp164 (D164) is the Na+-binding site, D163 controls the alternating accessibility of this binding site to the cytoplasm or periplasm, and D133 is crucial for pH regulation. Consistent with experimental stoichiometry, two protons are required to transport a single Na+ ion: D163 protonates to reveal the Na+-binding site to the periplasm, and subsequent protonation of D164 releases Na+. Additional mutagenesis experiments further validated the model.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arkin, Isaiah T -- Xu, Huafeng -- Jensen, Morten O -- Arbely, Eyal -- Bennett, Estelle R -- Bowers, Kevin J -- Chow, Edmond -- Dror, Ron O -- Eastwood, Michael P -- Flitman-Tene, Ravenna -- Gregersen, Brent A -- Klepeis, John L -- Kolossvary, Istvan -- Shan, Yibing -- Shaw, David E -- New York, N.Y. -- Science. 2007 Aug 10;317(5839):799-803.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉D. E. Shaw Research, New York, NY 10036, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17690293" target="_blank"〉PubMed〈/a〉
Keywords:
Aspartic Acid/metabolism
;
Binding Sites
;
Computer Simulation
;
Crystallization
;
Cytoplasm/metabolism
;
Escherichia coli/growth & development/*metabolism
;
Escherichia coli Proteins/*chemistry/*metabolism
;
Hydrogen Bonding
;
Hydrogen-Ion Concentration
;
Ion Transport
;
*Models, Biological
;
Models, Molecular
;
Mutagenesis
;
Periplasm/metabolism
;
Protein Conformation
;
Protein Structure, Secondary
;
*Protons
;
Sodium/*metabolism
;
Sodium-Hydrogen Antiporter/*chemistry/*metabolism
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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