Thioredoxin-insensitive plastid ATP synthase that performs moonlighting functions
Thioredoxin-insensitive plastid ATP synthase that performs moonlighting functions
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DOI：
10.1073/pnas.1115728109
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发表时间：
2012-02-28
影响因子：
11.1
通讯作者：
Kramer, David M.
中科院分区：
文献类型：
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作者：
Kohzuma, Kaori;Dal Bosco, Cristina;Kramer, David M.
叶绿体三磷酸腺苷合成酶催化光驱动的三磷酸腺苷合成，是光合作用的关键反馈调节成分。拟南芥具有由ATPC1和ATPC2基因编码的ATP合成酶调节性伽马亚基的两个同源基因。利用一系列突变体，我们证明了这两个亚基在体内都可以支持光合作用的ATP合成，但在野生型植物中，只有Gamma(1)参与光合作用中的ATP合成。含有Gamma(1)的ATP合成酶表现出经典的光诱导氧化还原调节，而只表达Gamma(2)-ATP合成酶(Gamma交换修正的ATP合成酶，Gamera)的突变体在光照和黑暗中表现出同样高的ATP合成酶活性。原位氧化还原滴定表明，在生理条件下，调节γ(2)-ATP合成酶的硫醇基团仍然是还原的，但可以被强氧化剂二胺氧化，这意味着伽马(2)中硫醇/二硫键转变的氧化还原电位大大高于伽马(1)中的氧化还原电位。这种调控差异可能归因于氧化还原活性硫醇附近残基的变化。我们认为，Gamma(2)-ATP合成酶在非光合体中催化ATP水解驱动的质子转运，维持足够的跨类囊体质子梯度来驱动蛋白质转运或其他过程。与这种解释一致的是，ATPC2主要在根中表达，而改变其表达会导致根毛发育的改变。系统发育分析表明，Gamma(2)起源于古老的基因复制，导致了双子叶植物和苔藓植物中不同功能的ATP合成酶复合体的不同进化。
The chloroplast ATP synthase catalyzes the light-driven synthesis of ATP and acts as a key feedback regulatory component of photosynthesis. Arabidopsis possesses two homologues of the regulatory gamma subunit of the ATP synthase, encoded by the ATPC1 and ATPC2 genes. Using a series of mutants, we show that both these subunits can support photosynthetic ATP synthesis in vivo with similar specific activities, but that in wild-type plants, only gamma(1) is involved in ATP synthesis in photosynthesis. The gamma(1)-containing ATP synthase shows classical light-induced redox regulation, whereas the mutant expressing only gamma(2)-ATP synthase (gamma exchange-revised ATP synthase, gamera) shows equally high ATP synthase activity in the light and dark. In situ redox titrations demonstrate that the regulatory thiol groups on gamma(2)-ATP synthase remain reduced under physiological conditions but can be oxidized by the strong oxidant diamide, implying that the redox potential for the thiol/disulphide transition in gamma(2) is substantially higher than that for gamma(1). This regulatory difference may be attributed to alterations in the residues near the redox-active thiols. We propose that gamma(2)-ATP synthase functions to catalyze ATP hydrolysis-driven proton translocation in nonphotosynthetic plastids, maintaining a sufficient transthylakoid proton gradient to drive protein translocation or other processes. Consistent with this interpretation, ATPC2 is predominantly expressed in the root, whereas modifying its expression results in alteration of root hair development. Phylogenetic analysis suggests that gamma(2) originated from ancient gene duplication, resulting in divergent evolution of functionally distinct ATP synthase complexes in dicots and mosses.