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Mechanism of NH4(+) Recruitment and NH3 Transport in Rh Proteins

Baday, Sefer and Orabi, Esam A. and Wang, Shihao and Lamoureux, Guillaume and Bernèche, Simon. (2015) Mechanism of NH4(+) Recruitment and NH3 Transport in Rh Proteins. Structure: with folding and design, Vol. 23, H. 8. S. 1550-1557.

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Official URL: http://edoc.unibas.ch/dok/A6428734

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Abstract

In human cells, membrane proteins of the rhesus (Rh) family excrete ammonium and play a role in pH regulation. Based on high-resolution structures, Rh proteins are generally understood to act as NH3 channels. Given that cell membranes are permeable to gases like NH3, the role of such proteins remains a paradox. Using molecular and quantum mechanical calculations, we show that a crystallographically identified site in the RhCG pore actually recruits NH4(+), which is found in higher concentration and binds with higher affinity than NH3, increasing the efficiency of the transport mechanism. A proton is transferred from NH4(+) to a signature histidine (the only moiety thermodynamically likely to accept a proton) followed by the diffusion of NH3 down the pore. The excess proton is circulated back to the extracellular vestibule through a hydrogen bond network, which involves a highly conserved and functionally important aspartic acid, resulting in the net transport of NH3.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Computational Biophysics (Bernèche)
UniBasel Contributors:Bernèche, Simon and Baday, Sefer
Item Type:Article, refereed
Bibsysno:Link to catalogue
Publisher:Current Biology
ISSN:0969-2126
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:02 Oct 2015 10:00
Deposited On:02 Oct 2015 10:00

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