1t9y
From Proteopedia
(New page: 200px<br /><applet load="1t9y" size="450" color="white" frame="true" align="right" spinBox="true" caption="1t9y, resolution 3.64Å" /> '''Structural Basis of ...) |
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| - | [[Image:1t9y.gif|left|200px]]<br /><applet load="1t9y" size=" | + | [[Image:1t9y.gif|left|200px]]<br /><applet load="1t9y" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1t9y, resolution 3.64Å" /> | caption="1t9y, resolution 3.64Å" /> | ||
'''Structural Basis of Multidrug Transport by the AcrB Multidrug Efflux Pump'''<br /> | '''Structural Basis of Multidrug Transport by the AcrB Multidrug Efflux Pump'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The Escherichia coli AcrB multidrug efflux pump is a membrane protein that | + | The Escherichia coli AcrB multidrug efflux pump is a membrane protein that recognizes many structurally dissimilar toxic compounds. We previously reported the X-ray structures of four AcrB-ligand complexes in which the ligands were bound to the wall of the extremely large central cavity in the transmembrane domain of the pump. Genetic studies, however, suggested that discrimination between the substrates occurs mainly in the periplasmic domain rather than the transmembrane domain of the pump. We here describe the crystal structures of the AcrB mutant in which Asn109 was replaced by Ala, with five structurally diverse ligands, ethidium, rhodamine 6G, ciprofloxacin, nafcillin, and Phe-Arg-beta-naphthylamide. The ligands bind not only to the wall of central cavity but also to a new periplasmic site within the deep external depression formed by the C-terminal periplasmic loop. This depression also includes residues identified earlier as being important in the specificity. We show here that conversion into alanine of the Phe664, Phe666, or Glu673 residue in the periplasmic binding site produced significant decreases in the MIC of most agents in the N109A background. Furthermore, decreased MICs were also observed when these residues were mutated in the wild-type AcrB background, although the effects were more modest. The MIC data were also confirmed by assays of ethidium influx rates in intact cells, and our results suggest that the periplasmic binding site plays a role in the physiological process of drug efflux. |
==About this Structure== | ==About this Structure== | ||
| - | 1T9Y is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with MC2 as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http:// | + | 1T9Y is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=MC2:'>MC2</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1T9Y OCA]. |
==Reference== | ==Reference== | ||
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[[Category: McDermott, G.]] | [[Category: McDermott, G.]] | ||
[[Category: Nikaido, H.]] | [[Category: Nikaido, H.]] | ||
| - | [[Category: Yu, E | + | [[Category: Yu, E W.]] |
[[Category: MC2]] | [[Category: MC2]] | ||
[[Category: 12 transmembranes]] | [[Category: 12 transmembranes]] | ||
[[Category: membrane protein]] | [[Category: membrane protein]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:11:26 2008'' |
Revision as of 13:11, 21 February 2008
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Structural Basis of Multidrug Transport by the AcrB Multidrug Efflux Pump
Overview
The Escherichia coli AcrB multidrug efflux pump is a membrane protein that recognizes many structurally dissimilar toxic compounds. We previously reported the X-ray structures of four AcrB-ligand complexes in which the ligands were bound to the wall of the extremely large central cavity in the transmembrane domain of the pump. Genetic studies, however, suggested that discrimination between the substrates occurs mainly in the periplasmic domain rather than the transmembrane domain of the pump. We here describe the crystal structures of the AcrB mutant in which Asn109 was replaced by Ala, with five structurally diverse ligands, ethidium, rhodamine 6G, ciprofloxacin, nafcillin, and Phe-Arg-beta-naphthylamide. The ligands bind not only to the wall of central cavity but also to a new periplasmic site within the deep external depression formed by the C-terminal periplasmic loop. This depression also includes residues identified earlier as being important in the specificity. We show here that conversion into alanine of the Phe664, Phe666, or Glu673 residue in the periplasmic binding site produced significant decreases in the MIC of most agents in the N109A background. Furthermore, decreased MICs were also observed when these residues were mutated in the wild-type AcrB background, although the effects were more modest. The MIC data were also confirmed by assays of ethidium influx rates in intact cells, and our results suggest that the periplasmic binding site plays a role in the physiological process of drug efflux.
About this Structure
1T9Y is a Single protein structure of sequence from Escherichia coli with as ligand. Full crystallographic information is available from OCA.
Reference
A periplasmic drug-binding site of the AcrB multidrug efflux pump: a crystallographic and site-directed mutagenesis study., Yu EW, Aires JR, McDermott G, Nikaido H, J Bacteriol. 2005 Oct;187(19):6804-15. PMID:16166543
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