1xxw

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Structure of zinc induced heterodimer of two calcium free isoforms of phospholipase A2 from Naja naja sagittifera at 2.7A resolution

Overview

The crystal structure of a zinc-induced heterodimer of two metal-free, isoforms of a cobra venom phospholipase A(2) has been determined at 2.7, angstroms resolution. The crystals belong to space group P4(1), with, unit-cell parameters a = b = 65.5, c = 58.4 angstroms, and have a single, dimer in the asymmetric unit. The structure has been refined to R(cryst), and R(free) factors of 0.188 and 0.232, respectively. The two isoforms, have a sequence identity of 82%. The zinc ion forms a fivefold, coordination with a trigonal bipyramidal geometry involving one O atom, each from Asp24 and Asn112 from molecule A and Asp24 from molecule B and, two water molecules. Both molecules of the dimer are inactive. Molecule A, is inactive because Arg31 (B) binds to Asp49 (A), while an acetate ion has, displaced the essential water molecule and interacts with His48 (A). On, the other hand, Arg31 (A) interacts with the calcium-binding loop of, molecule B, resulting in an altered conformation of the loop. The absence, of a calcium ion, loss of the essential water molecule and the altered, conformation of the calcium-binding loop may be the reasons for the loss, of activity of molecule B.

About this Structure

1XXW is a Protein complex structure of sequences from Naja sagittifera with ZN and ACY as ligands. Active as Phospholipase A(2), with EC number 3.1.1.4 Full crystallographic information is available from OCA.

Reference

Structure of the zinc-induced heterodimer of two calcium-free isoforms of phospholipase A2 from Naja naja sagittifera at 2.7 angstroms resolution., Jabeen T, Sharma S, Singh N, Singh RK, Verma AK, Paramasivam M, Srinivasan A, Singh TP, Acta Crystallogr D Biol Crystallogr. 2005 Mar;61(Pt 3):302-8. Epub 2005, Feb 24. PMID:15735340

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