Kohorn B D, Harel E, Chitnis P R, Thornber J P, Tobin E M
J Cell Biol. 1986 Mar;102(3):972-81. doi: 10.1083/jcb.102.3.972.
The precursor for a Lemna light-harvesting chlorophyll a/b protein (pLHCP) has been synthesized in vitro from a single member of the nuclear LHCP multigene family. We report the sequence of this gene. When incubated with Lemna chloroplasts, the pLHCP is imported and processed into several polypeptides, and the mature form is assembled into the light-harvesting complex of photosystem II (LHC II). The accumulation of the processed LHCP is enhanced by the addition to the chloroplasts of a precursor and a co-factor for chlorophyll biosynthesis. Using a model for the arrangement of the mature polypeptide in the thylakoid membrane as a guide, we have created mutations that lie within the mature coding region. We have studied the processing, the integration into thylakoid membranes, and the assembly into light-harvesting complexes of six of these deletions. Four different mutant LHCPs are found as processed proteins in the thylakoid membrane, but only one appears to have an orientation in the membrane that is similar to that of the wild type. No mutant LHCP appears in LHC II. The other two mutant LHCPs cannot be detected within the chloroplasts. We conclude that stable complex formation is not required for the processing and insertion of altered LHCPs into the thylakoid membrane. We discuss the results in light of our model.
浮萍光捕获叶绿素a/b蛋白（pLHCP）的前体已在体外由核LHCP多基因家族的一个成员合成。我们报道了该基因的序列。当与浮萍叶绿体一起温育时，pLHCP被导入并加工成几种多肽，成熟形式组装到光系统II（LHC II）的光捕获复合物中。通过向叶绿体中添加叶绿素生物合成的前体和辅因子，加工后的LHCP的积累得以增强。以类囊体膜中成熟多肽的排列模型为指导，我们在成熟编码区内产生了突变。我们研究了其中六个缺失突变体的加工、整合到类囊体膜中以及组装到光捕获复合物中的情况。在类囊体膜中发现四种不同的突变型LHCP作为加工后的蛋白质，但只有一种在膜中的方向似乎与野生型相似。在LHC II中未发现突变型LHCP。另外两种突变型LHCP在叶绿体内无法检测到。我们得出结论，改变的LHCP加工和插入类囊体膜不需要稳定的复合物形成。我们根据我们的模型讨论了结果。
