Structural Mechanism of Prestin-Membrane Mechanotransduction.

Sound frequency discrimination in mammals depends on the conformational transitions of prestin (SLC26A5), the piezoelectric motor in outer hair cells. The mechanism that enables prestin's electrically driven interconversion and its dependence on membrane mechanics, remains unresolved. Here, we show that membrane forces represent a strong driver of the same conformational changes generated by transmembrane voltage and stabilized by bound anions. Single particle cryo-EM structures of nanodisc-reconstituted prestin were obtained from varying lipid composition and membrane thickness. These structures show that membrane thinning biases prestin from a compact conformation to a fully expanded conformation, mimicking outer hair cell elongation/contraction during electromotility. In contrast, zebrafish SLC26A5 transporters undergo complete elevator movements with redistribution of areal changes across leaflets. The structures, together with mutagenesis, H/D exchange mass spectrometry data, and NLC measurements, offer a high-resolution understanding of how prestin translates membrane tension into charge and motor movement during sound-evoked vibrations, revealing a process of reciprocal electro-mechanical transduction essential for tuning cochlear amplification.