Interaction of melittin and phospholipase A2 with azobenzene-containing phospholipid.
Interactions of melittin and/or phospholipase A2 (PLA2) with circular dichroism (CD)-active phospholipid, bis(4'-n-octanoxyazobenzene-4-carboxyl)-L-alpha-phosphatidylcholin e (CDPC), were studied. In the presence of melittin at a lipid-to-melittin molar ratio (Ri) of 5, multilamellar dispersion, composed of CDPC and dipalmitoylphosphatidylcholine with a molar ratio of 1, underwent morphological change to form small melittin-lipid particles. When PLA2 was added to the melittin-lipid particles at 37 degrees C, the CD band at 222 nm exhibited a remarkable enhancement depending on Ri, indicating the formation of melittin-PLA2-lipid complex. After a 30 min incubation of melittin-PLA2-lipid complex at 45 degrees C in the presence of Ca2+, the CD band at 222 nm was still enhanced and a new positive band at 356 nm was observed. On the other hand, in the absence of Ca2+, the CD enhancement characteristic of melittin-PLA2-lipid complex disappeared after the incubation at 45 degrees C. These results suggest that the melittin-PLA2-lipid complex did not undergo any drastic morphological change upon PLA2-catalyzed hydrolysis of lipid, and that Ca2+ is indispensable in order that the melittin-PLA2-lipid complex remains intact and PLA2 exerts efficient hydrolytic activity in the melittin-PLA2-lipid complex.
Nishiya
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Artificial Cells & Organs Research Centre, McGill University, Montreal, PQ, Canada.
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002942:Circular Dichroism; D006868:Hydrolysis; D008555:Melitten / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2
D010713:Phosphatidylcholines; C064527:bis(4'-n-octanoxyazobenzene-4-carboxyl)phosphatidylcholine; D008555:Melitten; D015060:1,2-Dipalmitoylphosphatidylcholine; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium