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{{STRUCTURE_4m8j|  PDB=4m8j  |  SCENE=  }}
===Crystal structure of CaiT R262E bound to gamma-butyrobetaine===
{{ABSTRACT_PUBMED_24101465}}


==Function==
==Crystal structure of CaiT R262E bound to gamma-butyrobetaine==
[[http://www.uniprot.org/uniprot/C2LLR0_PROMI C2LLR0_PROMI]] Catalyzes the exchange of L-carnitine for gamma-butyrobetaine and related betaines (By similarity).[HAMAP-Rule:MF_01049]  
<StructureSection load='4m8j' size='340' side='right'caption='[[4m8j]], [[Resolution|resolution]] 3.29&Aring;' 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]] 3.294&#8491;</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.


==About this Structure==
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>
[[4m8j]] is a 1 chain structure with sequence from [http://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].


==Reference==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
<ref group="xtra">PMID:024101465</ref><references group="xtra"/><references/>
</div>
[[Category: Proteus mirabilis atcc 29906]]
<div class="pdbe-citations 4m8j" style="background-color:#fffaf0;"></div>
[[Category: Kalayil, S.]]
== References ==
[[Category: Cait]]
<references/>
[[Category: Carnitine/gamma-butyrobetaine antiporter]]
__TOC__
[[Category: Leut fold]]
</StructureSection>
[[Category: Plasma membrane]]
[[Category: Large Structures]]
[[Category: Transport protein]]
[[Category: Proteus mirabilis ATCC 29906]]
[[Category: Kalayil S]]
Retrieved from "https://proteopedia.org/4m8j"