Autopromotion of K-Ras4B feedback activation through an SOS-mediated long-range allosteric effect

X He, K Du, Y Wang, J Fan, M Li, D Ni, S Lu… - Frontiers in Molecular …, 2022 - frontiersin.org
X He, K Du, Y Wang, J Fan, M Li, D Ni, S Lu, X Bian, Y Liu
Frontiers in Molecular Biosciences, 2022frontiersin.org
The Ras-specific guanine nucleotide exchange factors Son of Sevenless (SOS) regulates
Ras activation by converting inactive GDP-bound to active GTP-bound states. The catalytic
activity of Ras is further allosterically regulated by GTP− Ras bound to a distal site through a
positive feedback loop. To address the mechanism underlying the long-range allosteric
activation of the catalytic K-Ras4B by an additional allosteric GTP–Ras through SOS, we
employed molecular dynamics simulation of the K-Ras4BG13D• SOScat complex with and …
The Ras-specific guanine nucleotide exchange factors Son of Sevenless (SOS) regulates Ras activation by converting inactive GDP-bound to active GTP-bound states. The catalytic activity of Ras is further allosterically regulated by GTP−Ras bound to a distal site through a positive feedback loop. To address the mechanism underlying the long-range allosteric activation of the catalytic K-Ras4B by an additional allosteric GTP–Ras through SOS, we employed molecular dynamics simulation of the K-Ras4BG13D•SOScat complex with and without an allosteric GTP-bound K-Ras4BG13D. We found that the binding of an allosteric GTP−K-Ras4BG13D enhanced the affinity between the catalytic K-Ras4BG13D and SOScat, forming a more stable conformational state. The peeling away of the switch I from the nucleotide binding site facilitated the dissociation of GDP, thereby contributing to the increased nucleotide exchange rate. The community networks further showed stronger edge connection upon allosteric GTP−K-Ras4BG13D binding, which represented an increased interaction between catalytic K-Ras4BG13D and SOScat. Moreover, GTP−K-Ras4BG13D binding transmitted allosteric signaling pathways though the Cdc25 domain of SOS that enhanced the allosteric regulatory from the K-Ras4BG13D allosteric site to the catalytic site. This study may provide an in-depth mechanism for abnormal activation and allosteric regulation of K-Ras4BG13D.
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