Electrostatic binding of proteins to membranes. Theoretical predictions and experimental results with charybdotoxin and phospholipid vesicles

Abstract

We previously applied the Poisson-Boltzmann equation to atomic models of phospholipid bilayers and basic peptides to calculate their electrostatic interactions from first principles (Ben-Tal, N., B. Honig, R. M. Peitzsch, G. Denisov, and S. McLaughlan. 1996. Binding of small basic peptides to membranes containing acidic lipids. Theoretical models and experimental results. Biophys. J. 71:561-575). Specifically, we calculated the molar partition coefficient, K (the reciprocal of the lipid concentration at which 1/2 the peptide is bound), of simple basic peptides (e.g., pentalysine) with phospholipid vesicles. The theoretical predictions agreed well with experimental measurements of the binding, but the agreement could have been fortuitous because the structure(s) of these flexible peptides is not known. Here we use the same theoretical approach to calculate the membrane binding of two small proteins of known structure: charybdotoxin (CTx) and iberiotoxin (IbTx); we also measure the binding of these proteins to phospholipid vesicles. The theoretical model describes accurately the dependence of K on the ionic strength and mol % acidic lipid in the membrane for both CTx (net charge +4) and IbTx (net charge +2). For example, the theory correctly predicts that the value of K for the binding of CTx to a membrane containing 33% acidic lipid should decrease by a factor of 10(5) when the salt concentration increases from 10 to 200 mM. We discuss the limitations of the theoretical approach and also consider a simple extension of the theory that incorporates nonpolar interactions.

β-Sheet Pore-Forming Peptides Selected from a Rational Combinatorial Library: Mechanism of Pore Formation in Lipid Vesicles and Activity in Biological Membranes

“…This is an infinite dilution measurement in which partition coefficients are independent of peptide concentration. However because there are electrostatic interactions, the values are dependent on experimental conditions such as ionic strength (41). All of the peptides studied here have similar membrane binding.…”

The Effector Domain of Myristoylated Alanine-rich C Kinase Substrate Binds Strongly to Phosphatidylinositol 4,5-Bisphosphate

“…To describe the binding of the peptide to lipid vesicles without making assumptions about the absorption mechanism, we use a molar partition coefficient, K, as described previously (38,39). …”

Biochemical characterization of the interaction between HspA1A and phospholipids

“…2). The expectation was that if HspA1A is peripherally associated with liposomes containing a particular lipid, then high levels of salt would decrease the amount of protein bound to the vesicles because high salt concentrations disrupt electrostatic and minimally hydrophobic interactions, but they will not affect proteins embedded in the bilayer (Ben-Tal et al 1997;Hanshaw et al 2008).…”