1now: Difference between revisions

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-[[Image:1now.gif|left|200px]]<br /><applet load="1now" size="350" color="white" frame="true" align="right" spinBox="true"
-caption="1now, resolution 2.20&Aring;" />
-'''Human lysosomal beta-hexosaminidase isoform B in complex with (2R,3R,4S,5R)-2-Acetamido-3,4-Dihydroxy-5-Hydroxymethyl-Piperidinium Chloride (GalNAc-isofagomine)'''<br />
-==Overview==
+==Human lysosomal beta-hexosaminidase isoform B in complex with (2R,3R,4S,5R)-2-Acetamido-3,4-Dihydroxy-5-Hydroxymethyl-Piperidinium Chloride (GalNAc-isofagomine)==
-In humans, two major beta-hexosaminidase isoenzymes exist: Hex A and Hex B. Hex A is a heterodimer of subunits alpha and beta (60% identity), whereas Hex B is a homodimer of beta-subunits. Interest in human beta-hexosaminidase stems from its association with Tay-Sachs and Sandhoff disease; these are prototypical lysosomal storage disorders resulting from the abnormal accumulation of G(M2)-ganglioside (G(M2)). Hex A degrades G(M2) by removing a terminal N-acetyl-D-galactosamine (beta-GalNAc) residue, and this activity requires the G(M2)-activator, a protein which solubilizes the ganglioside for presentation to Hex A. We present here the crystal structure of human Hex B, alone (2.4A) and in complex with the mechanistic inhibitors GalNAc-isofagomine (2.2A) or NAG-thiazoline (2.5A). From these, and the known X-ray structure of the G(M2)-activator, we have modeled Hex A in complex with the activator and ganglioside. Together, our crystallographic and modeling data demonstrate how alpha and beta-subunits dimerize to form either Hex A or Hex B, how these isoenzymes hydrolyze diverse substrates, and how many documented point mutations cause Sandhoff disease (beta-subunit mutations) and Tay-Sachs disease (alpha-subunit mutations).
+<StructureSection load='1now' size='340' side='right'caption='[[1now]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
+== Structural highlights ==
+<table><tr><td colspan='2'>[[1now]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NOW OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1NOW 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]] 2.2&#8491;</td></tr>
+<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=IFG:(2R,3R,4S,5R)-2-ACETAMIDO-3,4-DIHYDROXY-5-HYDROXYMETHYL-PIPERIDINE'>IFG</scene>, <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=1now FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1now OCA], [https://pdbe.org/1now PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1now RCSB], [https://www.ebi.ac.uk/pdbsum/1now PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1now ProSAT]</span></td></tr>
+</table>
+== Disease ==
+[https://www.uniprot.org/uniprot/HEXB_HUMAN HEXB_HUMAN] Defects in HEXB are the cause of GM2-gangliosidosis type 2 (GM2G2) [MIM:[https://omim.org/entry/268800 268800]; also known as Sandhoff disease. GM2-gangliosidosis is an autosomal recessive lysosomal storage disease marked by the accumulation of GM2 gangliosides in the neuronal cells. GM2G2 is clinically indistinguishable from GM2-gangliosidosis type 1, presenting startle reactions, early blindness, progressive motor and mental deterioration, macrocephaly and cherry-red spots on the macula.<ref>PMID:1720305</ref> <ref>PMID:1531140</ref> <ref>PMID:8357844</ref> <ref>PMID:7626071</ref> <ref>PMID:7557963</ref> <ref>PMID:7633435</ref> <ref>PMID:8950198</ref> <ref>PMID:9401004</ref> <ref>PMID:9856491</ref> <ref>PMID:9694901</ref>
+== Function ==
+[https://www.uniprot.org/uniprot/HEXB_HUMAN HEXB_HUMAN] Responsible for the degradation of GM2 gangliosides, and a variety of other molecules containing terminal N-acetyl hexosamines, in the brain and other tissues.
+== Evolutionary Conservation ==
+[[Image:Consurf_key_small.gif|200px|right]]
+Check<jmol>
+  <jmolCheckbox>
+    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/no/1now_consurf.spt"</scriptWhenChecked>
+    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
+    <text>to colour the structure by Evolutionary Conservation</text>
+  </jmolCheckbox>
+</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=1now ConSurf].
+<div style="clear:both"></div>
-==Disease==
+==See Also==
-Known diseases associated with this structure: Sandhoff disease, infantile, juvenile, and adult forms OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=606873 606873]], Spinal muscular atrophy, juvenile OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=606873 606873]]
+*[[Beta-Hexosaminidase|Beta-Hexosaminidase]]
+*[[Beta-Hexosaminidase 3D structures|Beta-Hexosaminidase 3D structures]]
-==About this Structure==
+*[[Beta-N-acetylhexosaminidase 3D structures|Beta-N-acetylhexosaminidase 3D structures]]
-NOW is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=IFG:'>IFG</scene> and <scene name='pdbligand=GOL:'>GOL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Beta-N-acetylhexosaminidase Beta-N-acetylhexosaminidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.52 3.2.1.52] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NOW OCA].
+== References ==
+<references/>
-==Reference==
+__TOC__
-Crystal structure of human beta-hexosaminidase B: understanding the molecular basis of Sandhoff and Tay-Sachs disease., Mark BL, Mahuran DJ, Cherney MM, Zhao D, Knapp S, James MN, J Mol Biol. 2003 Apr 11;327(5):1093-109. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=12662933 12662933]
+</StructureSection>
-[[Category: Beta-N-acetylhexosaminidase]]
 [[Category: Homo sapiens]]
-[[Category: Single protein]]
+[[Category: Large Structures]]
-[[Category: Cherney, M M.]]
+[[Category: Cherney MM]]
-[[Category: James, M N.G.]]
+[[Category: James MNG]]
-[[Category: Knapp, S.]]
+[[Category: Knapp S]]
-[[Category: Mahuran, D J.]]
+[[Category: Mahuran DJ]]
-[[Category: Mark, B L.]]
+[[Category: Mark BL]]
-[[Category: Zhao, D.]]
+[[Category: Zhao D]]
-[[Category: GOL]]
-[[Category: IFG]]
-[[Category: SO4]]
-[[Category: (beta/alpha)8-barrel]]
-[[Category: family 20 glycosidase]]
-[[Category: homodimer]]
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:08:23 2008''