Third calcium ion found in an inhibitor-bound phospholipase A2
K Sekar1, D Gayathri, D Velmurugan
1Bioinformatics Centre, Indian Institute of Science, Bangalore 560 012, India. sekar@physics.iisc.ernet.in
Summary
Researchers detailed the crystal structure of a bovine pancreatic phospholipase A2 triple mutant. This study identified a third calcium ion and novel surface loop conformations, offering new insights into enzyme dynamics and lipid metabolism.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Phospholipase A2 (PLA2) is a key lipolytic enzyme essential for lipid metabolism.
- It catalyzes the hydrolysis of phospholipids at the sn-2 position.
- Understanding PLA2 structure is crucial for elucidating its function.
Purpose of the Study:
- To determine the crystal structure of a triple mutant (K53,56,121M) of bovine pancreatic phospholipase A2.
- To investigate the structural impact of complexation with p-methoxybenzoic acid (anisic acid).
- To characterize novel structural features, including calcium ion coordination and surface loop conformations.
Main Methods:
- X-ray crystallography was employed to obtain the crystal structure at 1.7 A resolution.
- The study involved a triple mutant of bovine pancreatic phospholipase A2.
- Complexation with p-methoxybenzoic acid (anisic acid) was utilized.
Main Results:
- The crystal structure of the bovine pancreatic phospholipase A2 triple mutant complexed with anisic acid was determined.
- A third calcium ion, not previously observed in similar structures, was identified.
- Ordered surface loop residues (60-70) adopted unique conformations, differing from those in structures with a second calcium ion.
- Four Tris molecules were located, with two implicated in stabilizing the third calcium ion and influencing surface loop dynamics via hydrogen bonds.
Conclusions:
- The findings reveal a novel structural state of bovine pancreatic phospholipase A2, characterized by a third calcium ion and distinct surface loop conformations.
- The presence of Tris molecules suggests their role in modulating enzyme structure and potentially its catalytic activity.
- This structural information provides new insights into the mechanisms governing phospholipase A2 function and regulation.
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