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The role of individual cardiolipin species on stability and activity of transporter A (MgtA)

Weikum, J.; Subramani, S.; Van Dyck, J.; Sobott, F.; Morth, Jens Preben

Published in: European Biophysics Journal With Biophysics Letters

Publication date: 2019

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Citation (APA): Weikum, J., Subramani, S., Van Dyck, J., Sobott, F., & Morth, J. P. (2019). The role of individual cardiolipin species on stability and activity of Magnesium transporter A (MgtA). European Biophysics Journal With Biophysics Letters, 48(S1), S166-S166. [P-350].

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S166 European Biophysics Journal (2019) 48 (Suppl 1):S1–S264 S166

P-348 (O-109) Biophysical insights into membrane fission mediated by ESCRT-III V. Georgiev1, Y. Avalos-Padilla2, T. Robinson1, E. Orozco3, R. Lipowsky1, R. Dimova1. P-350 1Max Planck Institute of Colloids and Interfaces, Potsdam, Germany; 2Institute The role of individual cardiolipin species on stability and activity of for Bioengineering of Catalonia, Barcelona, Spain; 3Departamento de Magnesium transporter A (MgtA) Infectómica y Patogénesis Molecular, CINVESTAV IPN, Mexico, Mexico. J. Weikum1, S. Subramani2, J. Van Dyck3, F. Sobott4, J.P. Morth5. The endosomal sorting complex required for transport (ESCRT) engages in 1University of Oslo (UiO)/ Technical University of Denmark (DTU), Oslo, processes of membrane remodelling and fission, such as formation of Norway; 2University of Oslo, Oslo, Norway; 3Biomolecular & Analytical Mass multivesicular bodies, plasma membrane repair, neuron pruning, virus budding Spectrometry (BAMS), University of Antwerpen, Antwerpen, Belgium; 4The and autophagy as reviewed in [1]. The ESCRT machinery contains more than 15 Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, organized in four sub-complexes (ESCRT-0, ESCRT-I, ESCRT-II and United Kingdom; 5DTU Bioengineering, Technical University of Denmark, ESCRT-III), among which the ESCRT-III (composed by Vps2, Vps20, Vps24 Copenhagen, Denmark. and Vps32) is highly conserved across the eukaryotic lineage and mediates the Membrane proteins are defined by their environment, the lipid bilayer, and are processes required for membrane deformation and fission [2]. Membrane models in many cases actually present as -lipid complexes. For several cases, the such as giant unilamellar vesicles (GUVs) [3] can be employed to unravel the importance of specific phospholipids or sterols for optimal protein activity has ESCRT action in vitro, given the complexity and the number of proteins been documented [1]. However, in many cases, specific lipid interactions with involved. It has been recently shown that solely Vps20, Vps32 and Vps24 from membrane proteins have not been studied or the role of the lipid in activity, the phagocytic parasite E. histolytica are required to generate intraluminal stability or the folding process of the protein is not well understood. We aim to vesicles (ILVs) in GUVs [4]. However, the current models do not provide a study membrane protein - lipid interaction using the bacterial magnesium complete picture of the biophysical mechanisms by which the ESCRT-III transporter A (MgtA) as a model system. MgtA belongs to the P-type ATPases components reshape the membrane. Moreover, the role of the membrane material family, believed to transport Mg2+ from the periplasm into the [2]. The properties in tuning the ESCRT-III activity is unrevealed. In this study, we enzymatic function of MgtA is highly dependent on anionic phospholipids, observed for first time the consecutive action of the ESCRT-III proteins on a especially cardiolipin, and co-localization of MgtA with cardiolipin in E. coli single-vesicle level, combining GUVs and microfluidics. We characterized cells has been documented [3]. We have shown that MgtA selectively retrieves several mechanisms involved in the membrane remodelling by the ESCRT-III cardiolipin from a diverse lipid mixture and further, exhibits high selectivity on complex and the regulation of the protein activity. Namely, (i) increase in the specific cardiolipin species for its activity. However, the molecular basis for membrane tension results in distortion of the ESCRT-III scaffold in the cardiolipin activation and interaction with MgtA, remains unknown. We aim to intraluminal buds; (ii) the ESCRT-III proteins influence both the membrane further study the membrane-protein interaction with techniques, such as native stiffness and the spontaneous curvature, and thus control the size of the ILVs; mass spectrometry and enzymatic studies, to understand how MgtA and (iii) a membrane fluid-fluid phase separation was induced in the presence of the cardiolipin interact. ESCRT-III machinery, whereby the ILVs formed from the liquid-ordered phase. References References 1. Opekarová, M.; Tanner, W. (2003) Biochim Biophys Acta, 1610(1):11-22 [1] L. Christ et al., Trends Biochem. Sci., 2017, vol. 42, p. 42 2. Maguire, M.E. (1992) J Bioenerg Biomembr 24, 319-28 [2] J Schöneber et al., Nature Rev., 2017, vol. 18, p. 5 3. Subramani, S.; Perdreau-Dahl H.; Morth J.P. (2016) Elife, 5 [3] R. Dimova, Annu. Rev. Biophys., 2019, DOI: 10.1146/annurev-biophys- 052118-115342. [4] Y Avalos-Padilla et al., Front. Cell. Infect. Microbiol., 2018, vol. 8, p. 53 P-349 (O-110) Ion transport, interfacial effects and scaling behavior in protein channels V. Aguilella1, A. Alcaraz1, M. Aguilella-Arzo1, L. López-Peris1, M. Queralt- Martín2. 1Universitat Jaume I, Castellón, Spain; 2NICHD, National Institutes of Health, Bethesda MD, United States. Many protein channels have in common the importance of electrostatic interactions between the permeating ions and the nanochannel. Since ion transport occurs under confinement conditions, interfacial effects such as access resistance (AR) may play a significant role. We measure AR in a large , the bacterial OmpF, by means of single channel conductance measurements in solutions containing varying concentrations of high molecular weight PEG, sterically excluded from the pore. We found that AR might reach up to 80% of the total channel conductance in diluted solutions, where electrophysiological recordings register essentially the AR of the system and depend marginally on the pore characteristics. On the other hand, charged polar groups of the lipid may have a strong influence on the electric potential and the ionic concentration near the membrane-solution interface. Charged residues within the protein located near the pore mouth can also play a role, although to a lesser extent than AR and membrane surface charges. These three factors are obviously coupled and are strongly dependent on the channel aperture size, 3D structure and channel-lipid assembling. Comparison of experiments performed in charged and neutral planar membranes shows that lipid surface charges modify the ion distribution and determine the value of AR, indicating that lipid molecules are more than passive scaffolds even in the case of large transmembrane proteins. These findings are relevant to the fact that ionic conductance in membrane channels exhibits a power-law dependence on electrolyte concentration (G c). We critically evaluate the predictive power of scaling exponents by analyzing conductance measurements in four biological channels with contrasting architectures.∼ We show that scaling behavior depends on several interconnected effects whose contributions change with concentration so that the use of oversimplified models missing critical factors could be misleading. In fact, the presence of interfacial effects could give rise to an apparent universal scaling that hides the channel distinctive features. We complement our study with 3D structure-based Poisson−Nernst−Planck calculations, giving results in line with experiments and validating scaling arguments.

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