Karsten Kruse

Research

General

Living cells are fascinating beings. For example, they move, feed, grow, divide, and react to their environment. Furthermore, different cells can communicate with each other and may even form multi-cellular organisms.

These behaviors result from sub-cellular processes that arise through interactions between a large number of different proteins. There is good evidence that cells are internally organized in a modular way. Our research is aimed at understanding specific modules by analysing them as dynamical systems.

To this end we use methods from non-equilibrium statistical mechanics and non-linear dynamics. The guiding idea in this endeavour is to isolate essential components of a module, which then allows for an understanding of possible basic mechanisms underlying its function. This should lead to the identification of mechanisms that are common to different modules. The systems we are currently working on are the cytoskeleton of eucaryotic cells and the Min-system in Escherichia coli.

Min-Oscillations

An essential part of cell division is the determination of the division site. In Escherichia coli, a rod-shaped bacterium, division occurs with high precision in the middle, resulting in two equally sized daughter cells. Determination of the middle depends crucially on the Min-system.

This system consists of the proteins MinC, MinD, and MinE. Out of these, MinC is an unspecific inhibitor of division. The Min-proteins oscillate between the two cell poles with a period of about one minute. Thereby division is inhibited in the vicinity of the poles, but not inbetween. In addition to studying theoretical descriptions of possible mechanisms underlying the oscillations, we use fluorescence microscopy to quantitatively characterise the distributions of the Min-proteins in space and time.

Cytoskeleton

The cytoskeleton is a subcellular structure, which is for example important for cell division and for cell locomotion. It consists of filamentous protein assemblies, mostly actin filaments and microtubules, that interact through a number of different associated proteins. In particular, motor proteins like myosins or kinesins use the chemical energy stored in ATP to generate forces in the filament network.

Cells dispose of a variety of mechanisms to control and regulate the cytoskeleton. However, in vitro experiments have revealed the ability of motor-filament systems to self-organize.

We are interested in understanding, how much of the reorganisations of the cytoskeleton observed in living cells can be accounted for by self-organisation of cytoskeletal components. In addition, we study mechanical aspects of the cytoskeleton.