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Research

Research in the Stock Lab focusses on the structure and function of molecular rotary motors, which are fundamental components of all forms of life and contribute to biological energy conversion.

We are studying the vacuolar ATPase, a multi-subunit proton pump that occurs in the membranes of most intracellular compartments of eukaryotic cells. Fuelled by the biological energy carrier ATP, it pumps protons across these membranes resulting in a trans-membrane electrochemical proton gradient. The energy stored in this gradient is used to drive a variety of biological processes, such as neuro-transmitter uptake into synaptic vesicles and bone resorption into osteoclasts. Vacuolar ATPases are also important for intracellular pH homeostasis and for acidification of lysosomes. Eukaryotic vacuolar ATPases are extremely complex and fragile. We are therefore studying the evolutionary related A-type ATPase from the thermophilic bacterium Thermus thermophilus to gain insights into the stucture, molecular mechanisms and regulation of proton translocating ATPases. A-type ATPases are more stable when isolated but also more versatile than their eukaryotic relatives in that they can work in both directions: as proton-fuelled ATP synthases and as ATP-fuelled proton pumps depending on the cellular environment.

Another project involves structural studies of the bacterial flagellar motor and its components. Flagellated bacteria have hairlike structures attached to them, called flagella. Rotation of the flagella driven by the flagellar motor allows bacteria to swim from point A to point B. The flagellar motor is fuelled by a transmembrane electrochemical proton gradient. The flow of protons through the flagellar motor drives a rotation of the attached flagellum at thousands of revolutions per minute. Chemotactic signals from the cell's environment can reverse the sense of rotation from counterclockwise to clockwise thereby changing the swim-path from a straight line to a tumbling motion. This helps bacteria to steer towards favourable environments and away from unfavourable ones.