View source for 1li4


==Human S-adenosylhomocysteine hydrolase complexed with neplanocin==
<StructureSection load='1li4' size='340' side='right'caption='[[1li4]], [[Resolution|resolution]] 2.01&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1li4]] is a 1 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=1LI4 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1LI4 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]] 2.01&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=IPA:ISOPROPYL+ALCOHOL'>IPA</scene>, <scene name='pdbligand=NAD:NICOTINAMIDE-ADENINE-DINUCLEOTIDE'>NAD</scene>, <scene name='pdbligand=NOC:3-(6-AMINO-PURIN-9-YL)-5-HYDROXYMETHYL-CYCLOPENTANE-1,2-DIOL'>NOC</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=1li4 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1li4 OCA], [https://pdbe.org/1li4 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1li4 RCSB], [https://www.ebi.ac.uk/pdbsum/1li4 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1li4 ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/SAHH_HUMAN SAHH_HUMAN] Defects in AHCY are the cause of hypermethioninemia with S-adenosylhomocysteine hydrolase deficiency (HMAHCHD) [MIM:[https://omim.org/entry/613752 613752]. A metabolic disorder characterized by hypermethioninemia associated with failure to thrive, mental and motor retardation, facial dysmorphism with abnormal hair and teeth, and myocardiopathy.<ref>PMID:15024124</ref> <ref>PMID:16736098</ref> <ref>PMID:19177456</ref> <ref>PMID:20852937</ref> 
== Function ==
[https://www.uniprot.org/uniprot/SAHH_HUMAN SAHH_HUMAN] Adenosylhomocysteine is a competitive inhibitor of S-adenosyl-L-methionine-dependent methyl transferase reactions; therefore adenosylhomocysteinase may play a key role in the control of methylations via regulation of the intracellular concentration of adenosylhomocysteine.<ref>PMID:12590576</ref> 
== 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/li/1li4_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=1li4 ConSurf].
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== Publication Abstract from PubMed ==
S-Adenosylhomocysteine hydrolase (AdoHcy hydrolase) crystallizes from solutions containing the intermediate analogue neplanocin A with the analogue bound in its 3'-keto form at the active sites of all of its four subunits and the four tightly bound cofactors in their reduced (NADH) state. The enzyme is in the closed conformation, which corresponds to the structure in which the catalytic chemistry occurs. Examination of the structure in the light of available, very detailed kinetic studies [Porter, D. J., Boyd, F. L. (1991) J. Biol. Chem. 266, 21616-21625. Porter, D. J., Boyd, F. L. (1992) J. Biol. Chem. 267, 3205-3213. Porter, D. J. (1998) J. Biol. Chem. 268, 66-73] suggests elements of the catalytic strategy of AdoHcy hydrolase for acceleration of the reversible conversion of AdoHcy to adenosine (Ado) and homocysteine (Hcy). The enzyme, each subunit of which possesses a substrate-binding domain that in the absence of substrate is in rapid motion relative to the tetrameric core of the enzyme, first binds substrate and ceases motion. Probably concurrently with oxidation of the substrate to its 3'-keto form, the closed active site is "sealed off" from the environment, as indicated by a large (10(8)(-)(9)-fold) reduction in the rate of departure of ligands, a feature that prevents exposure of the labile 3'-keto intermediates to the aqueous environment. Elimination of the 5'-substituent (Hcy in the hydrolytic direction, water in the synthetic direction) generates the central intermediate 4',5'-didehydro-5'-deoxy-3'-ketoadenosine. Abortive 3'-reduction of the central intermediate is prevented by a temporary suspension of all or part of the redox catalytic power of the enzyme during the existence of the central intermediate. The abortive reduction is 10(4)-fold slower than the productive reductions at the ends of the catalytic cycle and has a rate constant similar to those of nonenzymic intramolecular model reactions. The mechanism for suspending the redox catalytic power appears to be a conformationally induced increase in the distance across which hydride transfer must occur between cofactor and substrate, the responsible conformational change again being that which "seals" the active site. The crystal structure reveals a well-defined chain of three water molecules leading from the active site to the subunit surface, which may serve as a relay for proton exchange between solvent and active site in the closed form of the enzyme, permitting maintenance of active-site functional groups in catalytically suitable protonation states.

Catalytic strategy of S-adenosyl-L-homocysteine hydrolase: transition-state stabilization and the avoidance of abortive reactions.,Yang X, Hu Y, Yin DH, Turner MA, Wang M, Borchardt RT, Howell PL, Kuczera K, Schowen RL Biochemistry. 2003 Feb 25;42(7):1900-9. PMID:12590576<ref>PMID:12590576</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 1li4" style="background-color:#fffaf0;"></div>

==See Also==
*[[S-adenosylhomocysteine hydrolase|S-adenosylhomocysteine hydrolase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Borchardt RT]]
[[Category: Howell PL]]
[[Category: Hu Y]]
[[Category: Kuczera K]]
[[Category: Schowen RL]]
[[Category: Turner MA]]
[[Category: Wang M]]
[[Category: Yang X]]
[[Category: Yin DH]]