Third calcium ion found in an inhibitor-bound phospholipase A2.
The lipolytic enzyme phospholipase A2 plays a crucial role in lipid metabolism and catalyzes hydrolysis of the fatty-acid ester bond at the sn-2 position of phospholipids. Here, the crystal structure (1.7 A resolution) of the triple mutant (K53,56,121M) of bovine pancreatic phospholipase A2 complexed with an organic molecule, p-methoxybenzoic acid (anisic acid), is reported. Residues 60-70 (the surface-loop residues) are ordered and adopt conformations which are different from those normally found in structures in which a second calcium ion is present. It is interesting to note that for the first time a third calcium ion has been identified. In addition, four Tris (2-amino-2-hydroxymethyl-1,3-propanediol) molecules were located. It is believed that one of the Tris molecules plays a role in clamping the third calcium ion and that another is involved in controlling the dynamics of the surface loop through hydrogen bonds.
Bioinformatics Centre, Indian Institute of Science, Bangalore 560 012, India. sekar@physics.iisc.ernet.in
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Sekar
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Gayathri
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Velmurugan
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Jeyakanthan
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Yamane
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Poi
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MD
Tsai
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D002413:Cations, Divalent / Q000737:chemistry; D002417:Cattle; D003460:Crystallization; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry*; D006860:Hydrogen Bonding; D062425:Hydroxybenzoate Ethers; D062385:Hydroxybenzoates / Q000737:chemistry; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010179:Pancreas / Q000201:enzymology; D010741:Phospholipases A / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D054467:Phospholipases A2; D017354:Point Mutation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D055672:Static Electricity; D014325:Tromethamine / Q000737:chemistry; D014867:Water / Q000737:chemistry
D002413:Cations, Divalent; D004791:Enzyme Inhibitors; D062425:Hydroxybenzoate Ethers; D062385:Hydroxybenzoates; D014325:Tromethamine; D014867:Water; C004520:4-anisic acid; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium