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1pp2
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(New page: 200px<br /><applet load="1pp2" size="450" color="white" frame="true" align="right" spinBox="true" caption="1pp2, resolution 2.5Å" /> '''THE REFINED CRYSTAL S...)
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Revision as of 21:52, 20 November 2007
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THE REFINED CRYSTAL STRUCTURE OF DIMERIC PHOSPHOLIPASE A2 AT 2.5 ANGSTROMS. ACCESS TO A SHIELDED CATALYTIC CENTER
Overview
The 2.5-A crystal structure of the calcium-free form of the dimeric venom, phospholipase A2 from the Western Diamondback rattlesnake Crotalus atrox, has been refined to an R-factor of 17.8% (I greater than 2 sigma) and, acceptable stereochemistry. The molecule is a nearly perfect 2-fold, symmetric dimer in which most of the catalytic residues of both subunits, face an internal cavity. The restricted access to the putative catalytic, sites is especially puzzling as the optimal substrates for this and most, other phospholipase A2 are phospholipids condensed in micellar or lamellar, aggregates. We point out that substrate access to the internal cavity may, be aided by calcium binding which can alter the intersubunit contacts that, shield the catalytic network. We also suggest that a system of, hydrogen-bonded moieties exists on the surface of the dimer that links the, amino terminus to the catalytic system, through an invariant Gln 4 side, chain and the backbone of the active center residue, Tyr 73. This, hydrogen-bonded network is on a highly accessible surface of the dimer and, would appear to contribute to the enzyme's (as opposed to the proenzyme's), special capacity to attack aggregated rather than monomeric substrate.
About this Structure
1PP2 is a Single protein structure of sequence from Crotalus atrox. Active as Phospholipase A(2), with EC number 3.1.1.4 Full crystallographic information is available from OCA.
Reference
The refined crystal structure of dimeric phospholipase A2 at 2.5 A. Access to a shielded catalytic center., Brunie S, Bolin J, Gewirth D, Sigler PB, J Biol Chem. 1985 Aug 15;260(17):9742-9. PMID:4019493
Page seeded by OCA on Tue Nov 20 23:59:15 2007
