TY - JOUR
T1 - A two-domain elevator mechanism for sodium/proton antiport
AU - Lee, Chiara
AU - Kang, Hae Joo
AU - Von Ballmoos, Christoph
AU - Newstead, Simon
AU - Uzdavinys, Povilas
AU - Dotson, David L.
AU - Iwata, So
AU - Beckstein, Oliver
AU - Cameron, Alexander D.
AU - Drew, David
N1 - Funding Information:
Acknowledgements We are grateful to D. Slotboom for critical reading of the manuscript and N.-J. Hu for assistance in data collection. Data were collected at the European Synchrotron Radiation Facility and Diamond Light Source, with excellent assistance from beamline scientists. This work was funded by grants from the Medical Research Council (MRC grant G0900990 to A.D.C. and D.D.), the Swedish Research Council (to C.v.B. and D.D.) and the BBSRC (BB/G02325/1 to S.I.). The authors are grateful for the use of the Membrane Protein Laboratory funded by the Wellcome Trust (grant 062164/Z/00/Z) at the Diamond Light Source Limited and The Centre for Biomembrane Research (CBR), supported by the Swedish Foundation for Strategic Research. Computer simulations were partially run on XSEDE resources (grant TG-MCB120151 to O.B.). C.L. was a recipient of a BBSRC-funded PhD scholarship, H.J.K. a Human Frontiers Science Program (HFSP) postdoctoral fellowship, and D.D. acknowledges the support from The Royal Society through the University Research Fellow (URF) scheme.
PY - 2013
Y1 - 2013
N2 - Sodium/proton (Na + /H +) antiporters, located at the plasma membrane in every cell, are vital for cell homeostasis. In humans, their dysfunction has been linked to diseases, such as hypertension, heart failure and epilepsy, and they are well-established drug targets. The best understood model system for Na + /H + antiport is NhaA from Escherichia coli, for which both electron microscopy and crystal structures are available. NhaA is made up of two distinct domains: a core domain and a dimerization domain. In the NhaA crystal structure a cavity is located between the two domains, providing access to the ion-binding site from the inward-facing surface of the protein. Like many Na + /H + antiporters, the activity of NhaA is regulated by pH, only becoming active above pH 6.5, at which point a conformational change is thought to occur. The only reported NhaA crystal structure so far is of the low pH inactivated form. Here we describe the active-state structure of a Na + /H + antiporter, NapA from Thermus thermophilus, at 3 Å resolution, solved from crystals grown at pH 7.8. In the NapA structure, the core and dimerization domains are in different positions to those seen in NhaA, and a negatively charged cavity has now opened to the outside. The extracellular cavity allows access to a strictly conserved aspartate residue thought to coordinate ion binding directly, a role supported here by molecular dynamics simulations. To alternate access to this ion-binding site, however, requires a surprisingly large rotation of the core domain, some 20against the dimerization interface. We conclude that despite their fast transport rates of up to 1,500 ions per second, Na + /H + antiporters operate by a two-domain rocking bundle model, revealing themes relevant to secondary-active transporters in general.
AB - Sodium/proton (Na + /H +) antiporters, located at the plasma membrane in every cell, are vital for cell homeostasis. In humans, their dysfunction has been linked to diseases, such as hypertension, heart failure and epilepsy, and they are well-established drug targets. The best understood model system for Na + /H + antiport is NhaA from Escherichia coli, for which both electron microscopy and crystal structures are available. NhaA is made up of two distinct domains: a core domain and a dimerization domain. In the NhaA crystal structure a cavity is located between the two domains, providing access to the ion-binding site from the inward-facing surface of the protein. Like many Na + /H + antiporters, the activity of NhaA is regulated by pH, only becoming active above pH 6.5, at which point a conformational change is thought to occur. The only reported NhaA crystal structure so far is of the low pH inactivated form. Here we describe the active-state structure of a Na + /H + antiporter, NapA from Thermus thermophilus, at 3 Å resolution, solved from crystals grown at pH 7.8. In the NapA structure, the core and dimerization domains are in different positions to those seen in NhaA, and a negatively charged cavity has now opened to the outside. The extracellular cavity allows access to a strictly conserved aspartate residue thought to coordinate ion binding directly, a role supported here by molecular dynamics simulations. To alternate access to this ion-binding site, however, requires a surprisingly large rotation of the core domain, some 20against the dimerization interface. We conclude that despite their fast transport rates of up to 1,500 ions per second, Na + /H + antiporters operate by a two-domain rocking bundle model, revealing themes relevant to secondary-active transporters in general.
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U2 - 10.1038/nature12484
DO - 10.1038/nature12484
M3 - Article
C2 - 23995679
AN - SCOPUS:84885576596
SN - 0028-0836
VL - 501
SP - 573
EP - 577
JO - Nature
JF - Nature
IS - 7468
ER -