4m8j: Difference between revisions
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The | ==Crystal structure of CaiT R262E bound to gamma-butyrobetaine== | ||
<StructureSection load='4m8j' size='340' side='right'caption='[[4m8j]], [[Resolution|resolution]] 3.29Å' scene=''> | |||
== Structural highlights == | |||
<table><tr><td colspan='2'>[[4m8j]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Proteus_mirabilis_ATCC_29906 Proteus mirabilis ATCC 29906]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4M8J OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4M8J FirstGlance]. <br> | |||
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 3.294Å</td></tr> | |||
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=NM2:3-CARBOXY-N,N,N-TRIMETHYLPROPAN-1-AMINIUM'>NM2</scene></td></tr> | |||
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=4m8j FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4m8j OCA], [https://pdbe.org/4m8j PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4m8j RCSB], [https://www.ebi.ac.uk/pdbsum/4m8j PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4m8j ProSAT]</span></td></tr> | |||
</table> | |||
== Function == | |||
[https://www.uniprot.org/uniprot/CAIT_PROMH CAIT_PROMH] Catalyzes the exchange of L-carnitine for gamma-butyrobetaine.[HAMAP-Rule:MF_01049]<ref>PMID:20829798</ref> <ref>PMID:24101465</ref> | |||
<div style="background-color:#fffaf0;"> | |||
== Publication Abstract from PubMed == | |||
Most secondary-active transporters transport their substrates using an electrochemical ion gradient. In contrast, the carnitine transporter (CaiT) is an ion-independent, l-carnitine/gamma-butyrobetaine antiporter belonging to the betaine/carnitine/choline transporter family of secondary transporters. Recently determined crystal structures of CaiT from Escherichia coli and Proteus mirabilis revealed an inverted five-transmembrane-helix repeat similar to that in the amino acid/Na+ symporter LeuT. The ion independence of CaiT makes it unique in this family. Here we show that mutations of arginine 262 (R262) make CaiT Na+-dependent. The transport activity of R262 mutants increased by 30-40% in the presence of a membrane potential, indicating substrate/Na+ cotransport. Structural and biochemical characterization revealed that R262 plays a crucial role in substrate binding by stabilizing the partly unwound TM1' helix. Modeling CaiT from P. mirabilis in the outward-open and closed states on the corresponding structures of the related symporter BetP reveals alternating orientations of the buried R262 sidechain, which mimic sodium binding and unbinding in the Na+-coupled substrate symporters. We propose that a similar mechanism is operative in other Na+/H+-independent transporters, in which a positively charged amino acid replaces the cotransported cation. The oscillation of the R262 sidechain in CaiT indicates how a positive charge triggers the change between outward-open and inward-open conformations as a unifying critical step in LeuT-type transporters. | |||
Arginine oscillation explains Na+ independence in the substrate/product antiporter CaiT.,Kalayil S, Schulze S, Kuhlbrandt W Proc Natl Acad Sci U S A. 2013 Oct 7. PMID:24101465<ref>PMID:24101465</ref> | |||
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.<br> | |||
</div> | |||
<div class="pdbe-citations 4m8j" style="background-color:#fffaf0;"></div> | |||
== References == | |||
<references/> | |||
__TOC__ | |||
</StructureSection> | |||
[[Category: Large Structures]] | |||
[[Category: Proteus mirabilis ATCC 29906]] | |||
[[Category: Kalayil S]] | |||
Latest revision as of 16:34, 20 September 2023
Crystal structure of CaiT R262E bound to gamma-butyrobetaine
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