A two-component molecular motor placing vesicles proximal to endosomal membranes. Credit: MPI-CBG
A cellular tethering protein switches to a flexible state when it binds to an active small signalling molecule1. This binding converts chemical energy into mechanical energy that is used to drag cargo-loaded vesicles inside a cell’s cytoplasm.
After unbinding from the small molecule, the protein reverts to a rigid state. The protein and small molecule generate force and act like a two-component molecular motor, says an international research team.
The scientists had previously shown that the tethering protein, known as EEA1, switched from a rigid, rod-like polymer to a flexible one after binding to an active signalling molecule, Rab5. This coupling converts the energy stored in guanosine triphosphate into mechanical work that is used in transporting and fusing vesicles with other molecular layers inside a cell.
The team, led by researchers at the National Centre for Biological Sciences, India, detected that EEA1 could reversibly undergo multiple flexibility transitions that were solely triggered by interaction with active Rab5. These transitions didn’t require any additional factors.
They also found that the motions of EEA1 were similar to that of a randomly moving polymer. Unlike classical engines, which work using gas and temperature difference, the two-component motor described here uses a polymer to generate force.
This kind of mechanism suggests new possibilities for the design of synthetic molecular engines, the researchers say.
