The transient membrane-engagement and reorientation of the soluble catalytic domain of Ras proteins has emerged as an important modulator of their functions. However, there has been limited information on whether this phenomenon is applicable to other members of the Ras superfamily. To address this issue, we conducted long-timescale atomistic molecular dynamics simulations (55µs aggregate simulation time) on representatives of the Ras, Rho and Arf family proteins that differ in sequence, lipid-modification, and the rigidity of the linker between the lipid anchor and the catalytic G-domain. The results show that the concept of membrane reorientation is generalizable to most but not all members of the Ras superfamily. Specifically, C-terminally prenylated small GTPases that are anchored to membranes via a single flexible linker adopt multiple orientations, whereas those N-terminally myristoylated and harbor a rigid linker experience limited orientational dynamics. Combined with published reports on Ras proteins, these observations provide insights into the common principles and determinants of the orientational dynamics of lipidated small GTPases on membrane surfaces, and offer new ways of thinking about the regulation and druggability of the Ras superfamily proteins.

Determinants of membrane orientation dynamics in lipid-modified small GTPases

ACS Spring 2022

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