PMID:15988517
| Citation |
Hunte, C, Screpanti, E, Venturi, M, Rimon, A, Padan, E and Michel, H (2005) Structure of a Na+/H+ antiporter and insights into mechanism of action and regulation by pH. Nature 435:1197-202 |
|---|---|
| Abstract |
The control by Na+/H+ antiporters of sodium/proton concentration and cell volume is crucial for the viability of all cells. Adaptation to high salinity and/or extreme pH in plants and bacteria or in human heart muscles requires the action of Na+/H+ antiporters. Their activity is tightly controlled by pH. Here we present the crystal structure of pH-downregulated NhaA, the main antiporter of Escherichia coli and many enterobacteria. A negatively charged ion funnel opens to the cytoplasm and ends in the middle of the membrane at the putative ion-binding site. There, a unique assembly of two pairs of short helices connected by crossed, extended chains creates a balanced electrostatic environment. We propose that the binding of charged substrates causes an electric imbalance, inducing movements, that permit a rapid alternating-access mechanism. This ion-exchange machinery is regulated by a conformational change elicited by a pH signal perceived at the entry to the cytoplasmic funnel. |
| Links |
PubMed Online version:10.1038/nature03692 |
| Keywords |
Binding Sites; Crystallography, X-Ray; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Hydrogen/metabolism; Hydrogen-Ion Concentration; Ion Transport; Models, Biological; Models, Molecular; Protein Conformation; Protons; Sodium/metabolism; Sodium-Hydrogen Antiporter/chemistry; Sodium-Hydrogen Antiporter/genetics; Sodium-Hydrogen Antiporter/metabolism; Static Electricity; Structure-Activity Relationship |
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