Sirpiö Sari, Allahverdiyeva Yagut, Holmström Maija, Khrouchtchova Anastassia, Haldrup Anna, Battchikova Natalia, Aro Eva-Mari
Department of Biology, Plant Physiology, and Molecular Biology, University of Turku, FI-20014 Turku, Finland.
J Biol Chem. 2009 Jan 9;284(2):905-12. doi: 10.1074/jbc.M805404200. Epub 2008 Oct 28.
The NAD(P)H dehydrogenase (NDH) complex functions in photosystem I cyclic electron transfer in higher plant chloroplasts and is crucial for plant responses to environmental stress. Chloroplast NDH complex is a close relative to cyanobacterial NDH-1L complex, and all fifteen subunits so far identified in NDH-1L have homologs in the chloroplast NDH complex. Here we report on the identification of two nuclear-encoded proteins NDH48 and NDH45 in higher plant chloroplasts and show their intimate association with the NDH complex. These two membrane proteins are shown to interact with each other and with the NDH complex enriched in stroma thylakoids. Moreover, the deficiency of either the NDH45 protein or the NDH48 protein in respective mutant plants leads to severe defects in both the accumulation and the function of the NDH complex. The NDH48 and NDH45 proteins are not components of the hydrophilic connecting domain of the NDH complex but are strongly attached to the hydrophobic membrane domain. We conclude that NDH48 and NDH45 are novel nuclear-encoded subunits of the chloroplast NDH complex and crucial both for the stable structure and function of the NDH complex.
NAD(P)H脱氢酶（NDH）复合体在高等植物叶绿体的光系统I循环电子传递中发挥作用，对植物应对环境胁迫至关重要。叶绿体NDH复合体与蓝藻NDH-1L复合体密切相关，目前在NDH-1L中鉴定出的所有15个亚基在叶绿体NDH复合体中都有同源物。在此，我们报道了在高等植物叶绿体中鉴定出两种核编码蛋白NDH48和NDH45，并展示了它们与NDH复合体的紧密关联。这两种膜蛋白相互作用，并与富集在基质类囊体中的NDH复合体相互作用。此外，各自突变植物中NDH45蛋白或NDH48蛋白的缺失都会导致NDH复合体的积累和功能出现严重缺陷。NDH48和NDH45蛋白不是NDH复合体亲水性连接域的组成部分，而是强烈附着于疏水性膜域。我们得出结论，NDH48和NDH45是叶绿体NDH复合体新的核编码亚基，对NDH复合体的稳定结构和功能都至关重要。
