軟体動物平滑筋形質膜局在Ca 結合蛋白質の微細構造観察

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原著It has been well established that the inner surface of plasma membrane in various smooth muscles plays a significant role in the storage and release of activator Ca，and it has also been suggested that a certain Ca‐binding protein localizes in the plasmamembrane. MCBP‐450 is a Ca‐binding protein isolated from plasma membrane fractions of the anterior byssus retractor muscle （ABRM） of Mytilus edulis．To elucidate the fine structure of this Ca‐binding protein，we observed purified molecules treated with the spray and low angle rotary shadowing (Spray‐LARS) method．In the replicas，the molecules showed a roughly ellipsoidal shape，the structural features of which were also observed in stereo images．The dimensions measured by a digital image processor were approximately 22 nm and 18 nm in long and short diameters，respectively. Furthermore, for direct visualization of these proteins，freeze‐fracture etching replicas of intact ABRM fibers frozen with liquid propane were examined．It was revealed that many granular structures corresponding to a part of the ellipsoidal Ca‐binding protein observed in Spray‐LARS replicas were localized along the inner surface of the plasma membrane．
2012-06-30