Twenty years after the identification of prestin, an anion transporter (SLC26) family member, as the lateral membrane motor protein of the outer hair cell (OHC), we are faced with the possibility of more fully understanding how this single molecule can influence the mammal’s exquisite sense of hearing. We propose to target a focused set of aims, including 1) determining the influence of mechanical load in governing prestin’s frequency dependence; simultaneous measures of sensor charge movement (complex NLC), electromotility are planned, 2) determining the effect of several cytoskeletal proteins on electromotility and charge movement and 3) ascertaining how the lipid and proteomic environment in the lateral wall changes along the tonotopic axis and its effects on sensor charge movement. In order to reach these goals, we will employ a host of genetic, electrophysiological, molecular biological and biochemical methods. We believe that the information that we obtain through these studies will aid in understanding how the OHC enables us to hear so well and in turn how we might combat pathologies of the OHC that afflict millions.