Department of Botany, University of Aberdeen, AB9 2UD, Aberdeen, UK.
Planta. 1974 Dec;118(4):271-81. doi: 10.1007/BF00385578.
Extracts of large quantities of petioles and of isolated vascular tissues of Heracleum mantegazzianum have been analysed for actomyosin-like contractile proteins. Concentrated preparations, subjected to a standard isolation and purification procedure for actomyosin, failed to demonstrate either superprecipitation or viscosity changes in response to the addition of ATP and divalent cations. In addition, ATPase activities in phloem and xylem extracts have been fractionated by gel electrophoresis and characterised with regard to their substrate specificity, pH optima and ion requirements. Phloem extracts provide two phosphatases: one is non-specific in its substrate requirements; the other is a nucleoside triphosphatase but is stimulated only by monovalent cations and is also present in xylem extracts. All the enzymes are strongly inhibited by divalent cations and do not possess any of the characteristics of ATPases associated with contractile systems. The results are discussed in relation to the postulated involvement of contractile proteins in the translocation of sugars in phloem.
已经分析了大量的芹菜叶柄和分离的血管组织提取物中的肌球蛋白样收缩蛋白。浓缩制剂经过肌球蛋白标准分离和纯化程序处理，在添加 ATP 和二价阳离子时既没有表现出超沉淀也没有表现出粘度变化。此外，通过凝胶电泳对韧皮部和木质部提取物中的 ATP 酶活性进行了分级，并根据其底物特异性、pH 最佳值和离子要求对其进行了描述。韧皮部提取物提供了两种磷酸酶：一种在其底物要求上是非特异性的；另一种是核苷三磷酸酶，但仅被单价阳离子刺激，也存在于木质部提取物中。所有的酶都被二价阳离子强烈抑制，并且不具有与收缩系统相关的 ATP 酶的任何特征。这些结果与收缩蛋白在韧皮部糖转运中假定的作用有关。
