简介：Prestinisthemotorproteinofcochlearouterhaircells(OHCs).ItisabletoperformrapidandreciprocalelectromechanicalconversionthatunderliesOHCelectromotility.Duetotheinadequatesizeofasingleprestinmoleculetoformthe~12nmintramembraneousproteinparticles(IMPs)intheOHClateralmembrane(LM),thepossibilityofprestinoligomerizationhasbeenproposed.Ithasbeensuggestedthatprestinmoleculesformhighorderoligomers,mostlikelyasthetetramer,inheterologoussystems.InOHCs,however,theoligomericstructureofprestinremainsunclear.Herewecalculatedtheprestin-relatedchargedensityinbothgerbilandguineapigOHCsthroughmeasuringtheirnonlinearcapacitance(NLC)andLMsurfacearea,showingthattheaveragechargedensity(22,608μm-2ingerbils;19,460μm-2inguineapigs)isstatistically4timestheaveragedensityofIMPs(5,686μm-2ingerbils;5,000μm-2inguineapigs).ThissuggeststhateachIMPcontainsfourprestinmoleculesbaseduponthenotionthateachprestintransfersasingleelementarycharge,implyingthatprestinformstetramersinOHCs.Todeterminewhethertheprestintetramerfunctionsasamechanicalunit,wesubsequentlycomparedtheslopefactors(α)ofelectromotilityandNLCsimultaneouslymeasuredfromthesameOHC,showingthattheαvaluesofthetwoarestatisticallythesame.ThissuggeststhateachprestinmoleculeinthetetramerismechanicallyindependentandequallycontributestoOHCelectromotility.