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1kju

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[[Image:1kju.gif|left|200px]]<br /><applet load="1kju" size="350" color="white" frame="true" align="right" spinBox="true"
 
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caption="1kju, resolution 6.00&Aring;" />
 
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'''Ca2+-ATPase in the E2 State'''<br />
 
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==Overview==
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==Ca2+-ATPase in the E2 State==
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Ca(2+)-ATPase is responsible for active transport of calcium ions across the sarcoplasmic reticulum membrane. This coupling involves an ordered sequence of reversible reactions occurring alternately at the ATP site within the cytoplasmic domains, or at the calcium transport sites within the transmembrane domain. These two sites are separated by a large distance and conformational changes have long been postulated to play an important role in their coordination. To characterize the nature of these conformational changes, we have built atomic models for two reaction intermediates and postulated the mechanisms governing the large structural changes. One model is based on fitting the X-ray crystallographic structure of Ca(2+)-ATPase in the E1 state to a new 6 A structure by cryoelectron microscopy in the E2 state. This fit indicates that calcium binding induces enormous movements of all three cytoplasmic domains as well as significant changes in several transmembrane helices. We found that fluorescein isothiocyanate displaced a decavanadate molecule normally located at the intersection of the three cytoplasmic domains, but did not affect their juxtaposition; this result indicates that our model likely reflects a native E2 conformation and not an artifact of decavanadate binding. To explain the dramatic structural effect of calcium binding, we propose that M4 and M5 transmembrane helices are responsive to calcium binding and directly induce rotation of the phosphorylation domain. Furthermore, we hypothesize that both the nucleotide-binding and beta-sheet domains are highly mobile and driven by Brownian motion to elicit phosphoenzyme formation and calcium transport, respectively. If so, the reaction cycle of Ca(2+)-ATPase would have elements of a Brownian ratchet, where the chemical reactions of ATP hydrolysis are used to direct the random thermal oscillations of an innately flexible molecule.
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<SX load='1kju' size='340' side='right' viewer='molstar' caption='[[1kju]], [[Resolution|resolution]] 6.00&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[1kju]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KJU OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1KJU FirstGlance]. <br>
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 6&#8491;</td></tr>
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<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1kju FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1kju OCA], [https://pdbe.org/1kju PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1kju RCSB], [https://www.ebi.ac.uk/pdbsum/1kju PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1kju ProSAT]</span></td></tr>
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</table>
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== Function ==
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[https://www.uniprot.org/uniprot/AT2A1_RABIT AT2A1_RABIT] This magnesium-dependent enzyme catalyzes the hydrolysis of ATP coupled with the translocation of calcium from the cytosol to the sarcoplasmic reticulum lumen. Contributes to calcium sequestration involved in muscular excitation/contraction (By similarity).
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== Evolutionary Conservation ==
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[[Image:Consurf_key_small.gif|200px|right]]
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Check<jmol>
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<jmolCheckbox>
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<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/kj/1kju_consurf.spt"</scriptWhenChecked>
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<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
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<text>to colour the structure by Evolutionary Conservation</text>
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</jmolCheckbox>
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</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1kju ConSurf].
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<div style="clear:both"></div>
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==About this Structure==
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==See Also==
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1KJU is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryctolagus_cuniculus Oryctolagus cuniculus]. Active as [http://en.wikipedia.org/wiki/Calcium-transporting_ATPase Calcium-transporting ATPase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.6.3.8 3.6.3.8] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KJU OCA].
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*[[ATPase 3D structures|ATPase 3D structures]]
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__TOC__
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==Reference==
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</SX>
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A structural model for the catalytic cycle of Ca(2+)-ATPase., Xu C, Rice WJ, He W, Stokes DL, J Mol Biol. 2002 Feb 8;316(1):201-11. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11829513 11829513]
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[[Category: Large Structures]]
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[[Category: Calcium-transporting ATPase]]
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[[Category: Oryctolagus cuniculus]]
[[Category: Oryctolagus cuniculus]]
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[[Category: Single protein]]
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[[Category: He W]]
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[[Category: He, W.]]
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[[Category: Rice WJ]]
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[[Category: Rice, W J.]]
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[[Category: Stokes DL]]
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[[Category: Stokes, D L.]]
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[[Category: Xu C]]
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[[Category: Xu, C.]]
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[[Category: active transport]]
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[[Category: calcium]]
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[[Category: cryo-em]]
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[[Category: e2]]
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[[Category: ion pump]]
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[[Category: membrane protein]]
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[[Category: p-type atpase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:34:56 2008''
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Current revision

Ca2+-ATPase in the E2 State

1kju, resolution 6.00Å

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