Gillespie P G, Wagner M C, Hudspeth A J
Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas 75235-9039.
Neuron. 1993 Oct;11(4):581-94. doi: 10.1016/0896-6273(93)90071-x.
By adapting to sustained stimuli, hair cells of the internal ear maintain their optimal sensitivity to minute displacements. Biophysical experiments have suggested that adaptation is mediated by a molecular motor, most likely a member of the myosin family. To provide direct evidence for the presence of myosin isozymes in hair bundles, we used photoaffinity labeling with vanadate-trapped uridine and adenine nucleotides to identify proteins of 120, 160, and 230 kd in a preparation of hair bundles purified from the bullfrog's sacculus. The photoaffinity labeling properties of these proteins, particularly the 120 kd protein, resembled those of other well-characterized myosins. A 120 kd hair-bundle protein was also recognized by a monoclonal antibody directed against a vertebrate myosin I isozyme. Immunofluorescence microscopy localized this protein near the beveled top edge of the hair bundle, the site of mechanoelectrical transduction and adaptation.
通过适应持续刺激，内耳毛细胞保持对微小位移的最佳敏感性。生物物理实验表明，适应是由分子马达介导的，最有可能是肌球蛋白家族的成员。为了直接证明毛束中存在肌球蛋白同工酶，我们使用钒捕获的尿苷和腺嘌呤核苷酸进行光亲和标记，以鉴定从牛蛙球囊纯化的毛束制剂中120、160和230kd的蛋白质。这些蛋白质，特别是120kd蛋白质的光亲和标记特性与其他特征明确的肌球蛋白相似。一种针对脊椎动物肌球蛋白I同工酶的单克隆抗体也识别出一种120kd的毛束蛋白。免疫荧光显微镜检查将该蛋白定位在毛束倾斜的顶部边缘附近，即机械电转导和适应的部位。
