A Full-Scaled Perspective of K-Ras4B Transformations Modulated by Oncogenic G12D and Phosphorylation in Phase-Segregated Membrane

K-Ras4B is known as the primary oncogenic protein, and increasing attention has been paid to reveal the critical conformation details for novelty of targeting drugs. K-Ras4B exits as a bioactive GTPase by anchoring on the cell membrane for signal transduction, which is closely implicated with the membrane environments and protein modifications/mutations. This study employed all-atom and coarse-grained molecular dynamic simulations to explore the membrane association and conformation switching mechanisms of K-Ras4B under the influence of the G12D mutation and the S181 phosphorylation (S181P) in a phase-segregated lipid bilayer. Compared with the wild-type (WT) and G12D which reside in the nonraft phase, S181P inclines to the lipid raft phase and presents as an inactive (S2) conformation mediated by the multivalent anionic lipids. The G12D mutation assists in the formation of the active (S1) state by exposing its acceptor-binding domain of Switch-I to the cytosolic region. This structure is established before membrane association verified by introducing a membrane-less model of the G12D mutant, and it is the resultant local electrostatic repulsion that elevates the structural flexibility and solvent accessibility of the Switch-I region. The multiscaled dynamic perspectives herein reveal inherent transformational mechanisms involving the intramolecular protein allostery details as well as the intermolecular membrane mediation, which is beneficial to further understand K-Ras4B in signal transduction and following anticancer drug novelty.