Anionic lipid membrane electrostatic potential and solution pH can influence cationic peptide adsorption to these bilayers, especially those containing simultaneously acid and basic residues. Here, we investigate the effects of the pH solution on MP1 (IDWKKLLDAAKQIL-NH2) adsorption to anionic (7POPC:3POPG) lipid vesicles in comparison to its analog H-MP1, with histidines substituting lysines. We used the association of adsorption isotherms and constant pH molecular dynamic simulations (CpHMD) to explore the effects of membrane potential and pH on peptides’ adsorption on this lipid membrane. We analyzed the fluorescence and zeta potential adsorption isotherms using the Gouy–Chapman theory. In CpHMD simulations for the peptides in solution and adsorbed on the lipid bilayer, we used the conformations obtained by conventional MD simulations at a μs timescale. Non-equilibrium Monte Carlo simulations provided the protonation states of acidic and basic residues. CpHMD showed average pKa shifts of two to three units, resulting in a higher net charge for the analog than for MP1, strongly modulating the peptide adsorption. The fractions of the protonation of acidic and basic residues and the peptides’ net charges obtained from the analysis of the adsorption isotherms were in reasonable agreement with those from CpHMD. MP1 adsorption was almost insensitive to solution pH. H-MP1 was much more sensitive to partitioning, at acidic pH, with an affinity ten times higher than in neutral ones.

The dysregulated activation of the Ras pathway is directly associated with approximately one-third of human cancer cases. The interaction between the adaptor protein GRB2 and the guanine nucleotide exchange factor SOS1 plays a crucial role in this process, serving as a key link in the activation of Ras. This interaction facilitates signal transduction that regulates essential cellular processes such as proliferation, survival, and differentiation and is, therefore, a central point in oncogenesis. Although the GRB2-SOS1 complex is critical for the regulation of Ras pathway signaling, the structural mechanisms governing this interaction remain largely unknown. In this study, we conducted an in-depth analysis of the interaction between GRB2 and peptides derived from SOS1, utilizing computational modeling, docking, and molecular dynamics simulations, combined with a detailed analysis of the energy landscape (ELViM). The results demonstrate that the conformational flexibility of the GRB2 protein has a direct impact on the stability of the GRB2-SOS1 complex, with communication between GRB2 domains being a determining factor for the robustness of this interaction. Additionally, we identified critical residues that play decisive roles in the formation and regulation of this interaction, which may serve as potential targets for modulation of the Ras pathway. These findings not only deepen the understanding of the structural mechanisms underlying the GRB2–SOS1 interaction but also provide a foundation for the development of specific therapeutic strategies aimed at controlling aberrant Ras pathway signaling, thereby offering new prospects in the treatment of diseases associated with the anomalous activation of Ras.