Biocenter, University of Basel, CH-4056 Basel, Switzerland.
Proc Natl Acad Sci U S A. 1980 Mar;77(3):1361-4. doi: 10.1073/pnas.77.3.1361.
The H(+)-translocating ATPase complex of chloroplasts consists of at least eight nonidentical subunits. Five of these (alpha, beta, gamma, delta, and epsilon subunits) collectively constitute the globular extramembranous CF(1) portion of the complex. The remaining three subunits (I-III) represent the membrane-embedded portion. Biosynthesis and assembly of these subunits were studied by pulse-labeling isolated spinach chloroplasts in the presence of cycloheximide or chloramphenicol and by translating total leaf RNA in a rabbit reticulocyte system. The labeled products were analyzed by immunoprecipitation with subunit-specific antisera or by isolating the entire H(+)-translocating ATPase complex in a nearly pure state. We found that chloroplasts synthesize the alpha, beta, gamma, and epsilon subunits of CF(1), the membrane-embedded subunit I, and probably also the membrane-embedded subunit III. The delta subunit (and probably also subunit II) are imported from the cytoplasm via larger precursor forms. After isolated chloroplasts are labeled in the presence of cycloheximide, the chloroplast-made H(+)-ATPase subunits are assembled into a complex that is indistinguishable from the authentic H(+)-ATPase complex. This assembly indicates that isolated chloroplasts contain excess pools of the cytoplasmically made subunits.
叶绿体的 H(+)-转运 ATP 酶复合物至少由八个非同源亚基组成。其中五个（α、β、γ、δ 和 ε 亚基）共同构成了该复合物球状的膜外 CF(1)部分。其余三个亚基（I-III）代表膜嵌入部分。通过在环己酰亚胺或氯霉素存在的情况下脉冲标记分离的菠菜叶绿体，以及在兔网织红细胞系统中转录总叶 RNA，研究了这些亚基的生物合成和组装。用亚基特异性抗血清进行免疫沉淀或在近乎纯的状态下分离整个 H(+)-转运 ATP 酶复合物来分析标记产物。我们发现叶绿体合成 CF(1)的α、β、γ和ε亚基、膜嵌入的亚基 I，可能还有膜嵌入的亚基 III。δ 亚基（可能还有亚基 II）通过较大的前体形式从细胞质中输入。在用环己酰亚胺标记分离的叶绿体后，叶绿体合成的 H(+)-ATP 酶亚基组装成一种与真实 H(+)-ATP 酶复合物无法区分的复合物。这种组装表明，分离的叶绿体含有细胞质中合成的亚基的过剩池。
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