Molecular engine resembling octopus tentacles found inside cells

Biophysicists from Germany and India have discovered a new molecular system that uses an alternative

chemical energy and uses a new mechanismto perform mechanical work. By repeatedly contracting and expanding, the two-component “motor” operates similarly to a classic Stirling engine and helps distribute cargo across membrane-bound organelles.

Cells have an amazing abilityneatly organize your interior space with tiny protein mechanisms called molecular motors that generate directional movements. Most of them use a common fuel, a kind of chemical energy, adenosine triphosphoric acid (ATP) to run.

In their study, the scientists examined the molecularan engine composed of two proteins, EEA1 and Rab5. These filamentous EEA1 proteins can recognize and bind to Rab5 present in the vesicle membrane. The binding sends a message along the elongated structure of the filamentous protein, thereby increasing its flexibility, similar to how cooking softens spaghetti. This change in flexibility creates a force that draws the vesicle to the target membrane where docking and fusion occurs.

Studying the work of this protein mechanism with the help ofusing laser scanning and light microscopes, the researchers showed that the EEA1 protein can go through several cycles of transition from rigid to flexible and back again solely due to the chemical energy released when it interacts with Rab5, without the use of ATP.

Researchers have developed a new physical modelto describe the relationship between chemical and mechanical steps in a molecular engine. They were also able to calculate the thermodynamic efficiency of the system, which is comparable to classical ATP-driven motor proteins.

This is a new class of molecular motors!It does not move around like a kinesin motor that transports cargo through microtubules, but does work by staying in place. It looks a bit like the tentacles of an octopus.

Stefan Grill, co-author of the study from the Institute for Molecular Cell Biology and Genetics of the Max Planck Society and the Technical University of Dresden

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On the cover: illustration of a two-component molecular engine. Image: MPI-CBG