Calcium-dependent association of annexins with lipid bilayers modifies gramicidin A channel parameters

Abstract

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.

Proteomic identification of an upregulated isoform of annexin A3 in the rat brain following reversible cerebral ischemia

“…Each of these annexins has a divergent N-terminal ''head'' which is variable and modulates protein binding (Hofmann et al, 2000;Sopkova et al, 2002), and a conserved C-terminal protein core which forms the calcium and membrane binding sites. In vitro, annexins have been implicated in membrane stabilization, ion channel activity (Eskesen et al, 2001), and mediation of membrane-membrane and membrane-cytoskeleton interaction (Diakonova et al, 1997). They also have a role in exocytosis and membrane trafficking and are associated with anti-inflammation and calcium-signaling mediators (Diakonova et al, 1997).…”

Applications of biological pores in nanomedicine, sensing, and nanoelectronics

“…Other approaches have demonstrated that single channel recordings can report molecular binding events. For instance, binding of proteins to lipids in a membrane typically affects the structure of the lipid bilayer and leads to changes in the kinetics of pore formation by biological pores such as gramicidin [195,303]. Using this effect, Hirano et al detected antibody binding to antigen-decorated lipids (Figure 9b) [195].…”

“…Using this effect, Hirano et al detected antibody binding to antigen-decorated lipids (Figure 9b) [195]. Another study by Bennekou and co-workers monitored calcium-dependent binding of the peripheral membrane protein annexin [83,304] to lipid membranes; in this case, the resulting changes in the lifetime and single channel conductance of gramicidin pores provided the signal [303]. …”

Immobilizing Single Lipid and Channel Molecules in Artificial Lipid Bilayers with Annexin A5

“…The single RyR2 molecule electrophysiological results with and without 1 μM annexin A5 show that annexin A5 has minimal effect on either the open probability (Po) or conductance (Figure ). In contrast, Eskesen et al reported that annexin A5 decreases the conductance of gramicidin A, concluding diffusion resistance increases in the gramicidin A channel mouth . This is likely because gramicidin A has a small cylindrical radius in the transmembrane region, meaning annexin A5 binding to the lipid can easily access the ion pathway of this peptide channel.…”