1hn4

<StructureSection load='1hn4' size='340' side='right' caption='[[1hn4]], [[Resolution|resolution]] 1.50&Aring;' scene=''>

<table><tr><td colspan='2'>[[1hn4]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Pig Pig]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1HN4 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1HN4 FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=MJI:1-HEXADECYL-3-TRIFLUOROETHYL-SN-GLYCERO-2-PHOSPHATE+METHANE'>MJI</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene></td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Phospholipase_A(2) Phospholipase A(2)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.1.1.4 3.1.1.4] </span></td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1hn4 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1hn4 OCA], [http://pdbe.org/1hn4 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1hn4 RCSB], [http://www.ebi.ac.uk/pdbsum/1hn4 PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1hn4 ProSAT]</span></td></tr>

[[http://www.uniprot.org/uniprot/PA21B_PIG PA21B_PIG]] PA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides.

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== Publication Abstract from PubMed ==

Kinetic results in this paper show that, contrary to earlier reports, pig pancreatic prophospholipase A(2) (proPLA2) does not hydrolyze monodisperse short chain phosphatidylcholine below the critical micelle concentration. ProPLA2 is active on an anionic interface, but at a rate that is decreased by more than 100-fold compared to that of PLA2, the active form. Solution studies show that both proPLA2 and PLA2 bind to an anionic interface and also bind a tetrahedral intermediate mimic at the active site. The 1.5 A resolution crystal structure of the anion-assisted dimer of proPLA2 reported in this paper is compared with the corresponding structure for PLA2 [Pan, Y. H., et al. (2001) Biochemistry 40, 609-617]. As a mimic for the forms bound to the anionic interface, these structures provide insights into the possible structural basis for the impaired chemical step of the zymogen. The proPLA2 dimer contained within one crystallographic asymmetric unit has one molecule of the inhibitor 1-hexadecyl-3-(trifluoroethyl)-sn-glycero-2-phosphomethanol and is bridged by four coplanar sulfate anions. Relative to the structure of PLA2, the subunit contact surface in proPLA2 displays a tilted orientation, an altered mode of inhibitor binding, displacement of a mechanistically significant loop that includes Tyr69, and a critical active site water seen in PLA2 that is not seen in proPLA2. These differences are interpreted to suggest possible origins of the functional differences between the pro and active enzyme at an anionic interface. A structural origin of this difference is discussed in terms of the calcium-coordinated activated water mechanism of the esterolysis reaction. Together, a comparison of the structures of the anion-assisted dimers of PLA2 and proPLA2 not only offers an explanation of why the zymogen form is k(cat)-impaired and binds poorly even to the anionic interface but also supports a mechanism for the activated enzyme that includes a critical second-sphere assisting water bridging His48 and the calcium-coordinated catalytic water.

 

== References ==

[[Category: Pig]]

[[Category: Bahnson, B J]]

[[Category: Epstein, T M]]

[[Category: Jain, M K]]

[[Category: Pan, Y H]]

[[Category: Carboxylic ester hydrolase]]

[[Category: Sulfate binding]]