Inhibition of outer hair cell electromotility by sulfhydryl specific reagents

Mammalian outer hair cells can change length at acoustic frequencies when they are electrically stimulated. It was postulated that these length changes depend on electromechanical transduction based on voltage dependent conformational changes in a membrane motor protein. In this report, we describe the effect of various sulfhydryl (SH)-specific reagents on the OHC electromotility. p-Chloromercuriphenylsulfonate (pCMPS), in addition to other mercurials that can react with well-protected SH-groups in proteins, inhibits this electromechanical transduction process. In contrast, N-ethylmaleimide and diamide, SH-reagents that only react with exposed SH-groups, showed no effect. These results suggest that one or more reactive SH-groups are present in a functionally important and protected region of the electromechanical transduction protein. Such reactivity can be utilized to identify and characterize this novel membrane motor.