Pomorski, T. | bioRxiv Science

bioRxiv2025

Sterols govern membrane susceptibility to saponin-induced lysis

Saponins are natural detergents that interact with cellular membranes, causing deterioration leading to membrane disruption. The magnitude of these effects depends on both the saponin structure and target membrane composition, where sterols play a key modulating role in saponin-membrane interaction. We investigated the influence of different sterol classes on saponin-induced membrane lysis. The bioactive, cytotoxic saponin -hederin induced permeability in membranes containing zoosterol and mycosterol, whereas phytosterol-containing membranes were resistant to lysis in vitro. Similarly, in yeast, -hederin caused significant cell lysis, while in the ergosterol-deficient erg3{Delta} and pdr18{Delta} mutants, cell lysis was minimal. Supplementing phytosterols to yeast provided resistance to -hederin-induced lysis. Molecular dynamics simulations provide novel mechanistic insights, showing that the efficacy of the activity of -hederin is proportional to the sterol type in the membrane. Our findings reveal that while zoosterols and mycosterols render membranes vulnerable to bioactive saponins, phytosterols protect membranes from saponin-induced lysis in vitro, in vivo and in silico.

molecular biology↗

bioRxiv2021

Mg2+-dependent conformational equilibria in CorA: an integrated view on transport regulation

The CorA family of proteins regulates the homeostasis of divalent metal ions in many bacteria, archaea, and eukaryotic mitochondria, making it an important target in the investigation of the mechanisms of transport and its functional regulation. Although numerous structures of open and closed channels are now available for the CorA family, the mechanism of the transport regulation remains elusive. Here, we investigated the conformational distribution and associated dynamic behaviour of the pentameric Mg2+ channel CorA at room temperature using small-angle neutron scattering (SANS) in combination with molecular dynamics (MD) simulations and solid-state nuclear magnetic resonance spectroscopy (NMR). We find that neither the Mg2+-bound closed structure nor the Mg2+-free open forms are sufficient to explain the average conformation of CorA. Our data support the presence of conformational equilibria between multiple states, and we further find a variation in the behaviour of the backbone dynamics with and without Mg2+. We propose that CorA must be in a dynamic equilibrium between different non-conducting states, both symmetric and asymmetric, regardless of bound Mg2+ but that conducting states become more populated in Mg2+-free conditions. These properties are regulated by backbone dynamics and are key to understanding the functional regulation of CorA.

biophysics↗