Calcium-dependent association of annexins with lipid bilayers modifies gramicidin A channel parameters.
In order to examine whether calcium-dependent binding of annexin to acidic phospholipids could change the lipid bilayer environment sufficiently to perturb channel-mediated transmembrane ion-transport, gramicidin A channel activity in planar lipid bilayers was investigated in the presence of calcium and annexins II, III or V. The experiments were performed with membranes consisting of phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine in 300 mM KCl solution buffered to pH 7.4 and with either 0.1 or 1 mM calcium added to the solution. Annexin (1 microM) was subsequently applied to the cis side of the membrane. All three annexins (II, III and V) when tested at 1 mM calcium decreased the gramicidin single-channel conductance. Annexins II and III increased the mean lifetime of the channels whereas annexin V seemed to have no influence on the mean lifetime. Since the lifetime of gramicidin A channels is a function of the rate constant for dissociation of the gramicidin dimer, which is dependent on the physical properties of the lipid phase, binding of annexins II and III seems to stabilize the gramicidin channel owing to a change of the bilayer structure.
Eskesen
K
K
August Krogh Institute, University of Copenhagen, Universitetsparken 13, 2100 Copenhagen Ø, Denmark.
Kristensen
B I
BI
Jørgensen
A J
AJ
Kristensen
P
P
Bennekou
P
P
D000818:Animals; D017306:Annexin A2 / Q000737:chemistry; D017318:Annexin A3 / Q000737:chemistry; D017304:Annexin A5 / Q000737:chemistry; D017302:Annexins / Q000737:chemistry* / Q000302:isolation & purification; D002118:Calcium; D002286:Carcinoma, Ehrlich Tumor; D002417:Cattle; D006096:Gramicidin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry*; D008168:Lung; D051379:Mice; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D011189:Potassium Chloride; D013552:Swine
D017306:Annexin A2; D017304:Annexin A5; D017302:Annexins; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D006096:Gramicidin; D011189:Potassium Chloride; D017318:Annexin A3; D002118:Calcium