Molecular engine inside cells
Scientists have reported the discovery of a new type of molecular engine that converts energy into motion. The study was published in the journal Nature Physics.Biophysicists from Germany and India have discovered a new molecular system that uses alternative chemical energy and applies a new mechanism to perform mechanical work. By repeatedly contracting and expanding, the two-component "motor" works similarly to the classical Stirling engine and helps distribute the load to membrane-associated organelles.
Cells have an amazing ability to neatly organize their internal space using tiny protein mechanisms, called molecular motors, which generate directional movements. Most of them use a common kind of fuel, a kind of chemical energy, adenosine triphosphoric acid (ATP), to work.
In their study, the scientists studied a molecular motor composed of two proteins, EEA1 and Rab5. These filamentous EEA1 proteins can recognize Rab5 present in the vesicle membrane and bind to it. Binding sends a message along the elongated structure of the filamentous protein, thereby increasing its flexibility, similar to the way cooking softens spaghetti. This change in flexibility creates a force that draws the vesicle to the target membrane, where docking and fusion occur.
By studying how this protein mechanism works using 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 by the chemical energy released during its interaction with Rab5, without the use of ATP.
The researchers developed a new physical model to describe the relationship between the chemical and mechanical steps in the molecular engine. They were also able to calculate the thermodynamic efficiency of the system, which is comparable to classical motor proteins driven by ATP.