Strzalka K, Ngernprasirtsiri J, Watanabe A, Akazawa T
Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University, Japan.
Biochem Biophys Res Commun. 1987 Dec 16;149(2):799-806. doi: 10.1016/0006-291x(87)90438-4.
Amyloplasts isolated from white-wild suspension-cultured cells of sycamore (Acer pseudoplatanus L.) are found to import and process the precursor of the small subunit (pS) of ribulose-1,5-bisphosphate carboxylase/oxygenase of spinach, but they lack the ability to form its holoenzyme due to the absence of both the large subunit and its binding-protein. They also import the precursor of the 33-kDa extrinsic protein (p33-kDa) of the O2-evolving complex of Photosystem II from spinach, but process is only to an intermediate form (i33-kDa). Chloroplasts from green-mutant cells of sycamore process p33-kDa to its mature form in this heterologous system. These results suggest that the thylakoid-associated protease responsible for the second processing step of p33-kDa is missing in amyloplasts, possibly due to the absence of thylakoid-membranes. In contrast, the apparent import of the precursor of the light-harvesting chlorophyll a/b-binding apoprotein (pLHCP) from spinach was not detected. Sycamore amyloplasts may lack the ability to import this particular thylakoid-protein, or rapidly degrade the imported molecules in the absence of thylakoid-membranes for their proper insertion.
从悬铃木（Acer pseudoplatanus L.）白色野生悬浮培养细胞中分离出的造粉体能够导入并加工菠菜核酮糖-1,5-二磷酸羧化酶/加氧酶小亚基（pS）的前体，但由于缺少大亚基及其结合蛋白，它们缺乏形成全酶的能力。它们还能导入菠菜光系统II放氧复合体33-kDa外在蛋白（p33-kDa）的前体，但加工后仅形成中间形式（i33-kDa）。在这个异源系统中，悬铃木绿色突变体细胞的叶绿体将p33-kDa加工成其成熟形式。这些结果表明，造粉体中缺少负责p33-kDa第二步加工的类囊体相关蛋白酶，这可能是由于缺少类囊体膜所致。相反，未检测到菠菜光捕获叶绿素a/b结合脱辅基蛋白（pLHCP）前体的明显导入。悬铃木造粉体可能缺乏导入这种特定类囊体蛋白的能力，或者在缺少类囊体膜以进行正确插入的情况下迅速降解导入的分子。
