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The Min proteins from E.coli position the bacterial cell-division machinery through pole-to-pole oscillations. In vitro, Min protein self-organization can be reconstituted in the presence of a lipid membrane as a catalytic surface. However, Min dynamics have so far not been reconstituted in fully membrane-enclosed volumes. Microdroplets interfaced by lipid monolayers were employed as a simple 3D mimic of cellular compartments to reconstitute Min protein oscillations. We demonstrate that lipid monolayers are sufficient to fulfil the catalytic role of the membrane and thus represent a facile platform to investigate Min protein regulated dynamics of the cell-division protein FtsZ-mts. In particular, we show that droplet containers reveal distinct Min oscillation modes, and reveal a dependence of FtsZ-mts structures on compartment size. Finally, co-reconstitution of Min proteins and FtsZ-mts in droplets yields antagonistic localization, thus demonstrating that droplets indeed support the analysis of complex bacterial self-organization in confined volumes. [ABSTRACT FROM AUTHOR]

Sich selbstorganisierende Muster aus gereinigten Min‐Proteinen – räumlichen Regulatoren der bakteriellen Zellteilung – und dem Zellteilungsprotein FtsZ wurden bei der Rekonstitution der Proteine in Emulsionströpfchen beobachtet, wie P. Schwille et al. in der Zuschrift auf S. 13653 ff. berichten. Das Bild zeigt FtsZ‐Filamentbündel (blau) und Min‐Proteine (rot) im Innern eines Tröpfchens. Eine Lipidmonoschicht (grün) bildet die Grenzfläche der Tröpfchen (Bild: G. Chwastek). [ABSTRACT FROM AUTHOR]

Self‐organizing patterns of purified Min proteins, which are spatial regulators of bacterial cell division, and the cell division protein FtsZ were observed when the proteins were reconstituted in emulsion droplets, as reported by P. Schwille and co‐workers in their Communication on page 13455 ff. The cover illustrates FtsZ filament bundles (blue) and Min proteins (red) in the lumen of a droplet, with a lipid monolayer (green) at the droplet interface (image by G. Chwastek). [ABSTRACT FROM AUTHOR]

Giant unilamellar vesicles (GUVs) represent a versatile in vitro system widely used to study properties of lipid membranes and their interaction with biomacromolecules and colloids. Electroformation with indium tin oxide (ITO) coated coverslips as electrodes is a standard approach to GUV production. In the case of cationic GUVs, however, application of this approach leads to notorious difficulties. We discover that this is related to aging of ITO-coated coverslips during their repeated use, which is reflected in their surface topography on the nanoscale. We find that mild annealing of the ITO-coated surface in air reverts the effects of aging and ensures efficient reproducible electroformation of supergiant (diameter > 100 μm) unilamellar vesicles containing cationic lipids.

The plasma membrane of cells can be viewed as a highly dynamic, regulated, heterogeneous environment with multiple functions. It constitutes the boundary of the cell, encapsulating all its components. Proteins interact with the membrane in many ways to accommodate essential processes, such as membrane trafficking, membrane protrusions, cytokinesis, signaling, and cell-cell communication. A vast amount of literature has already fostered our current understanding of membrane-protein interactions. However, many phenomena still remain to be understood, e.g., the exact mechanisms of how certain proteins cause or assist membrane transformations. Systems biology aims to predict biological processes on the basis of the set of molecules involved. Many key processes arise from interactions with the lipid membrane. Protein interactome maps do not consider such specific interactions, and thus cannot predict precise outcomes of the interactions of the involved proteins. These can only be inferred from experimental approaches. We describe examples of how an emergent behavior of protein-membrane interactions has been demonstrated by the use of minimal systems. These studies contribute to a deeper understanding of protein interactomes involving membranes and complement other approaches of systems biology., (Copyright © 2010 John Wiley & Sons, Inc.)