Binding of small basic peptides to membranes containing acidic lipids: theoretical models and experimental results

Abstract

We measured directly the binding of Lys3, Lys5, and Lys7 to vesicles containing acidic phospholipids. When the vesicles contain 33% acidic lipids and the aqueous solution contains 100 mM monovalent salt, the standard Gibbs free energy for the binding of these peptides is 3, 5, and 7 kcal/mol, respectively. The binding energies decrease as the mol% of acidic lipids in the membrane decreases and/or as the salt concentration increases. Several lines of evidence suggest that these hydrophilic peptides do not penetrate the polar headgroup region of the membrane and that the binding is mainly due to electrostatic interactions. To calculate the binding energies from classical electrostatics, we applied the nonlinear Poisson-Boltzmann equation to atomic models of the phospholipid bilayers and the basic peptides in aqueous solution. The electrostatic free energy of interaction, which arises from both a long-range coulombic attraction between the positively charged peptide and the negatively charged lipid bilayer, and a short-range Born or image charge repulsion, is a minimum when approximately 2.5 A (i.e., one layer of water) exists between the van der Waals surfaces of the peptide and the lipid bilayer. The calculated molar association constants, K, agree well with the measured values: K is typically about 10-fold smaller than the experimental value (i.e., a difference of about 1.5 kcal/mol in the free energy of binding). The predicted dependence of K (or the binding free energies) on the ionic strength of the solution, the mol% of acidic lipids in the membrane, and the number of basic residues in the peptide agree very well with the experimental measurements. These calculations are relevant to the membrane binding of a number of important proteins that contain clusters of basic residues.

PKC‐α controls MYD88‐dependent TLR/IL‐1R signaling and cytokine production in mouse and human dendritic cells

“…This is furthermore in line with the simultaneous timing and phoshorylation of MARCKS, an established PKC target also at the cell membrane. It is worth mentioning that phosphorylation of MARCKS by PKC leads to their detachment from the plasma membrane, which unmasks and increases the accessible lipid second messenger, PIP 2 , and is important for the activation of downstream signaling events [35][36][37]. Thus, our findings suggest that cPKC may play a more global role in TLR2-induced cellular processes and control phagocytosis, cytoskeletal changes and other signaling events.…”

Kinetics of Interaction of the Myristoylated Alanine-rich C Kinase Substrate, Membranes, and Calmodulin

“…1) with Ca 2ϩ ⅐CaM located above the peptide in the aqueous phase (see Ref. 39 for theoretical methodology). The calculations (data not shown) illustrate that the basic residues of the peptide can gain electrostatic energy from negatively charged Ca 2ϩ ⅐CaM before relinquishing completely their electrostatic interaction with the negatively charged membrane; the long-range nature of the electrostatic interactions could thus facilitate a rapid sequential desorption of the basic residues from the membrane by Ca 2ϩ ⅐CaM, giving rise to the rapid kinetics illustrated in Fig.…”

“…Thus, we compared the binding kinetics of K151C-MARCKS-(151-175) with those of heptalysine, a simpler peptide. The available data suggest that basic peptides such as heptalysine do not penetrate the lipid head group region and associate with membranes through nonspecific electrostatic interactions (38,39); thus, the binding kinetics of C-K 7 should be diffusion-limited. Fig.…”

Lateral Sequestration of Phosphatidylinositol 4,5-Bisphosphate by the Basic Effector Domain of Myristoylated Alanine-rich C Kinase Substrate Is Due to Nonspecific Electrostatic Interactions

“…GRASP, however, is capable of solving only the linearized version of the Poisson-Boltzmann equation. In order to represent accurately the electrostatic properties of the MARCKS-(151-175)/membrane systems, we solved the nonlinear Poisson-Boltzmann (NLPB) equation (33,51,64,69,70) for atomic models of these systems in 100 mM KCl on a finite difference grid of size 65 3 and used focusing boundary conditions (51) to a final resolution of 0.5 grid/Å. The resulting potential maps as well as the atomic coordinates for the MARCKS-(151-175)/membrane models were then read into GRASP and displayed on an SGI Octane Work station.…”

“…5B). A theoretical model explaining why the binding of basic peptides to membranes containing monovalent acidic lipids depends on salt concentration is given elsewhere (33,51). Briefly, increasing the salt concentration screens the charges on the membrane interface and thus decreases the magnitude of the negative electrostatic potential experienced by the basic peptide at the membrane surface.…”