Each person's hearing is provided by 'microscopic accordion'

Scientists at Oregon Health & Science University have determined the structure of the protein that makes us hear the world around us. It took them several years and tens of millions of worms to figure out the structure of the TMC-1 protein, which senses acoustic vibrations. The researchers published their paper in the journal Nature.

Before we hear sound, acoustic waves cause the eardrum to vibrate. Through several ossicles, these movements are transmitted to fluid-filled structures in the inner ear. Fluid vibrations are sensed by hair cells, which stimulate neurons and trigger the transmission of signals through the nervous system.

A key role in the work of the hair cells are transmembrane channel-like proteins (Transmembrane Channel-Like Proteins, TMC): they capture the mechanical vibrations, triggering the electrical signals in the nervous system. Scientists were able to establish the molecular structure of the TMC1 protein with the accuracy of individual atoms.

Biologists used worms Caenorhabditis elegans to obtain the TMC1 protein. Scientists needed more than five years, during which they grew and used about 60 million nematodes. The pure protein preparation was examined using cryo-electron microscopy to figure out the molecular structure of TMS-1.

TMS-1 is a transmembrane protein that permeates the cell membrane. It is a dimer consisting of a pair of identical blocks. Each dimer includes the key domain of TMS-1, which forms a pore in the membrane, as well as the calcium-binding domain of CALM-1 bound to TMS-1 from inside the cell. Finally, a small TMIE domain - in the words of the authors, "resembling accordion handles" - is attached to the molecule at the periphery. Mechanical deformation of the cell membrane triggers the entire system to work, causing calcium ions to flow inside the cell. This causes it to release neurotransmitters and stimulate auditory neuronal activity.

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