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| {{STRUCTURE_1zcd| PDB=1zcd | SCENE= }} | | {{STRUCTURE_1zcd| PDB=1zcd | SCENE= }} |
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| '''Crystal structure of the Na+/H+ antiporter NhaA'''
| | ===Crystal structure of the Na+/H+ antiporter NhaA=== |
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| ==Overview==
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| 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. | | The line below this paragraph, {{ABSTRACT_PUBMED_15988517}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15988517 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_15988517}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Antiporter]] | | [[Category: Antiporter]] |
| [[Category: Membrane protein]] | | [[Category: Membrane protein]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 17:27:29 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 04:22:09 2008'' |