Bauerle C, Dorl J, Keegstra K
Department of Botany, University of Wisconsin, Madison 53706.
J Biol Chem. 1991 Mar 25;266(9):5884-90.
The transport of the lumenal protein plastocyanin has been proposed to occur in two steps: 1) transport across the chloroplastic envelope to the stroma and 2) transport across the thylakoid membrane to the lumen where proteolytic maturation occurs. A partially processed stromal form of plastocyanin has been tentatively identified as a pathway intermediate and as the substrate for the second translocation step (Smeekens, S., Bauerle, C., Hageman, J., Keegstra, K., and Weisbeek, P. (1986) Cell 46, 365-375). In this study, we have examined the transport kinetics of several lumenal proteins under various incubation conditions. Soluble intermediate sized forms were observed in import reactions with plastocyanin precursors from three higher plant species and with the precursor of the 33-kDa polypeptide of the oxygen-evolving enhancer complex. The accumulation patterns observed for these soluble intermediate sized forms depended on incubation conditions and could not be consistently explained by a simple model where the intermediate sized form is the substrate for the second step. Thus, it has not been possible to clearly identify the substrate for thylakoid translocation in organello.
有人提出，腔内蛋白质体蓝素的转运分两步进行：1）穿过叶绿体被膜转运至基质；2）穿过类囊体膜转运至发生蛋白水解成熟的腔中。一种部分加工的基质形式的质体蓝素已被初步鉴定为途径中间体以及第二步转运步骤的底物（斯米肯斯，S.，鲍勒尔，C.，哈格曼，J.，基格斯特拉，K.，和韦斯贝克，P.（1986年）《细胞》46卷，365 - 375页）。在本研究中，我们检测了几种腔内蛋白在不同孵育条件下的转运动力学。在与来自三种高等植物物种的质体蓝素前体以及放氧增强复合物33 kDa多肽的前体的导入反应中，观察到了可溶性中等大小形式。这些可溶性中等大小形式的积累模式取决于孵育条件，并且不能用一个简单的模型来一致解释，该模型认为中等大小形式是第二步的底物。因此，在细胞器中尚未能够明确鉴定类囊体转运的底物。
