Protein Patterns and Oscillations on Lipid Monolayers and in Microdroplets

Abstract

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.

Beating Vesicles: Encapsulated Protein Oscillations Cause Dynamic Membrane Deformations

“…Consistent with previous observations for Min dynamics within microdroplets, [10] we observed two types of standing wave patterns and circling traveling waves (Figure 2 A-I). Consistent with previous observations for Min dynamics within microdroplets, [10] we observed two types of standing wave patterns and circling traveling waves (Figure 2 A-I).…”

“…[8] In further research, Min protein patterns were confined within SLBlined microfluidic scaffolds to probe geometry sensing and recreate spatial properties of bacterial cells. [10] Unfortunately, owing to the surface tension at the water-oil interphase, microdroplets are still very rigid compartments, and the difference in the refractive indices between the two phases hampers confocal imaging of the full 3D volume of the droplets. In a continuing attempt to confine the Min system to more cell-like compartments, we recently fully enclosed the proteins in microdroplets and were able to observe pole-topole oscillations on the lipid monolayer at the water-oil interface, similar to the oscillations seen in E. coli.…”

Sterol transfer, PI 4P consumption, and control of membrane lipid order by endogenous OSBP

“…On a large membrane network, these oscillations propagate leading to out of phase traveling waves between OSBP and PI4KIIa. Of note, this behavior is reminiscent of that of the Min system in Bacteria (Zieske et al, 2016) and of actin-based structures at the PM (Xiong et al, 2016). In the former case, time-dependent oscillations are inherent of the ATPase cycle of Min proteins and the wave pattern depends on the size of the supporting membrane system.…”

Microfluidic trapping of vesicles reveals membrane-tension dependent FtsZ cytoskeletal re-organisation

“…Examples of more biological meaningful compartments have been reported, such as polymersomes or giant unilamellar vesicles (GUVs). 8,19 We and others have also reconstituted Min protein patterns in more cell-like settings, such as in PDMS microcompartments, [20][21][22] in lipid droplets 23 , on the outside of lipid vesicles, 24 and inside lipid vesicles 25 . However, bacteria are not spherical, and it is clear that cell shape has a great impact on the boundary conditions of these processes.…”