1ceh
From Proteopedia
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STRUCTURE AND FUNCTION OF THE CATALYTIC SITE MUTANT ASP99ASN OF PHOSPHOLIPASE A2: ABSENCE OF CONSERVED STRUCTURAL WATER
Overview
To probe the role of the Asp-99 ... His-48 pair in phospholipase A2 (PLA2), catalysis, the X-ray structure and kinetic characterization of the mutant, Asp-99-->Asn-99 (D99N) of bovine pancreatic PLA2 was undertaken. Crystals, of D99N belong to the trigonal space group P3(1)21 and were isomorphous to, the wild type (WT) (Noel JP et al., 1991, Biochemistry 30:11801-11811)., The 1.9-A X-ray structure of the mutant showed that the carbonyl group of, Asn-99 side chain is hydrogen bonded to His-48 in the same way as that of, Asp-99 in the WT, thus retaining the tautomeric form of His-48 and the, function of the enzyme. The NH2 group of Asn-99 points away from His-48., In contrast, in the D102N mutant of the protease enzyme trypsin, the NH2, group of Asn-102 is hydrogen bonded to His-57 resulting in the inactive, tautomeric form and hence the loss of enzymatic activity. Although the, geometry of the catalytic triad in the PLA2 mutant remains the same as in, the WT, we were surprised that the conserved structural water, linking the, catalytic site with the ammonium group of Ala-1 of the interfacial site, was ejected by the proximity of the NH2 group of Asn-99. The NH2 group now, forms a direct hydrogen bond with the carbonyl group of Ala-1.
About this Structure
1CEH is a Single protein structure of sequence from Bos taurus with CA as ligand. Active as Phospholipase A(2), with EC number 3.1.1.4 Full crystallographic information is available from OCA.
Reference
Structure and function of the catalytic site mutant Asp 99 Asn of phospholipase A2: absence of the conserved structural water., Kumar A, Sekharudu C, Ramakrishnan B, Dupureur CM, Zhu H, Tsai MD, Sundaralingam M, Protein Sci. 1994 Nov;3(11):2082-8. PMID:7703854
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