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.
Sekar
K
K
Bioinformatics Centre, Indian Institute of Science, Bangalore 560 012, India. sekar@physics.iisc.ernet.in
Gayathri
D
D
Velmurugan
D
D
Jeyakanthan
J
J
Yamane
T
T
Poi
M J
MJ
Tsai
M D
MD
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