Penetration of the insect defensin A into phospholipid monolayers and formation of defensin A-lipid complexes.
Defensin A is an inducible cationic protein secreted in the hemolymph of fleshfly Phormia terranovae larvae in response to bacterial or septic injuries. Defensin A is known to permeabilize the bacteria cell membranes by forming voltage-dependent channels. The penetration of this small protein into lipid monolayers was studied as a function of the polar head and acyl chain length of phospholipids. The extent of penetration by defensin A is higher in monolayers made of anionic phospholipids than in monolayers made of zwitterionic phospholipids (phosphatidylcholines), because of electrostatic interactions. From the analysis of the compression isotherm parameters of mixed defensin A/phospholipid monolayers, it appears that defensin A interacts with phospholipid by forming 1:4 complexes. These complexes are not miscible in the lipid phase and induce microheterogeneity in the lipid membrane. These clusters might be related to the ion-channel structures responsible for the biological activity of defensin A.
Maget-Dana
R
R
Centre de Biophysique Moléculaire CNRS, Orléans, France.
Ptak
M
M
D000818:Animals; D002463:Cell Membrane Permeability; D002942:Circular Dichroism; D023082:Defensins; D004175:Diptera; D019476:Insect Proteins / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000378:metabolism; D055672:Static Electricity; D013499:Surface Properties
D023082:Defensins; D019476:Insect Proteins; D007473:Ion Channels; D008081:Liposomes; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D010743:Phospholipids; D011994:Recombinant Proteins; C058181:insect defensin A