Third calcium ion found in an inhibitor-bound phospholipase A2

✍ Scribed by Sekar, K. ;Gayathri, D. ;Velmurugan, D. ;Jeyakanthan, J. ;Yamane, T. ;Poi, M.-J. ;Tsai, M.-D.

• Book ID: 104478194
• Publisher: International Union of Crystallography
• Year: 2006
• Tongue: English
• Weight: 865 KB
• Volume: 62
• Category: Article
• ISSN: 0907-4449
• DOI: 10.1107/s0907444906001612

✦ Synopsis

The lipolytic enzyme phospholipase A 2 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 A 2 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.