Cryo-EM Structures of Prestin and the Molecular Basis of Outer Hair Cell Electromotility

The voltage-dependent motor protein, Prestin (SLC26A5) is responsible for the electromotive behavior of outer hair cells (OHCs). Here, we determined the structure of dolphin Prestin in complex with Cl- and the inhibitor Salicylate using single particle cryo-electron microscopy. These structures establish the specific structural features of mammalian Prestin and reveal small but significant differences with the transporter members of the SLC26 family of membrane proteins. Comparison with SLC26A9 point to conformational differences in the special relationship between the core and gate domains. Importantly, we highlight substantial alterations to the hydrophobic footprint of Prestin as it relates to the membrane, which point to a potential influence of Prestin on its surrounding lipid. The structure of Prestin bound to the inhibitor Salicylate confirms the nature of the anion binding pocket, formed by TM3 and TM10 in the Core domain and a set of anion coordinating residues which include Q97, F101, F137, S398 and R399. The presence of a well-defined density for Salycilate points to an inhibition mechanism based on competition for the anion-binding pocket of Prestin. These observations illuminate the structural basis of Prestin electromotility, a key component in the mammalian cochlear amplifier.