The Structural Basis of the Farnesylated and Methylated KRas4B Interaction with Calmodulin
59 Pages Posted: 11 Jul 2019 Publication Status: PublishedMore...
Ca2+-CaM extracts KRas4B from the plasma membrane, suggesting that KRas4B–CaM interaction plays a role in regulating Ras signaling. To gain mechanistic insight, we provide a computational model, supported by experimental structural data, of farnesylated/methylated KRas4B1-185-GTP interacting with CaM in solution and at anionic membranes including signaling lipids. Due to multiple interaction modes, we observe diverse conformational ensembles of the KRas4B–CaM complex. A highly populated conformation reveals the catalytic domain interacting with the N-lobe and the HVR wrapping around the linker with the farnesyl docking to the extended CaM’s C-lobe pocket. Alternatively, KRas4B can interact with collapsed CaM with the farnesyl penetrating CaM’s center. At anionic membranes, CaM interacts with the catalytic domain with large fluctuations that draw the HVR. Signaling lipids establishing strong salt bridges with CaM can prevent membrane departure. Membrane-interacting KRas4B–CaM complex can productively recruit PI3Kα to the plasma membrane, serving as a coagent in activating PI3Kα/Akt signaling.
Keywords: post-translational modifications, farnesylation and methylation, phosphatidylinositol, PIP2, NMR, MD simulation, SAXS, PI3K
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