The RNA-binding protein RNP29 is an unusual Toc159 transport substrate
The RNA-binding protein RNP29 is an unusual Toc159 transport substrate
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DOI：
10.3389/fpls.2014.00258
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发表时间：
2014-06-16
影响因子：
5.6
通讯作者：
Baginsky, Sacha
中科院分区：
文献类型：
--
作者：
Grimmer, Julia;Roediger, Anja;Baginsky, Sacha
RNP 29和铁氧还蛋白（Fd 2）的前体先前在ppi 2植物细胞的胞质溶胶中被鉴定，其N-末端氨基酸被乙酰化。在这里，我们探讨前体积累ppi 2是否是Toc 159客户端蛋白的特征，通过表征的RNP 29前体相比，Fd 2和其他Toc 159依赖或独立的底物的进口性能。我们发现RNP 29前体在ppi 2中特异性积累，但在野生型或peptide原生质体中没有。除Lhcb 4外，在ppi 2中的所有其他测试构建体中也检测到前体积累。然而，RNP 29与其他蛋白质明显不同，因为在原生质体提取物中仅检测到前体蛋白而几乎没有检测到成熟蛋白。RN P29与Toc 159的共转化补充了其质体输入，支持RN P29是Toc 159依赖性底物的假设。RNP 29转运肽中的第二个氨基酸交换为Glu或Asn阻止甲硫氨酸切除，但不阻止N-末端乙酰化，这表明不同的N-乙酰基转移酶可能在体内作用于叶绿体前体蛋白。所有不同的RNP 29构建体都被有效地导入野生型，但没有导入ppi 2质体，这说明N-末端氨基酸对导入过程的影响很小。
The precursors of RNP29 and Ferredoxin (Fd2) were previously identified in the cytosol of ppi2 plant cells with their N-terminal amino acid acetylated. Here, we explore whether precursor accumulation in ppi2 is characteristic for Toc159 client proteins, by characterizing the import properties of the RNP29 precursor in comparison to Fd2 and other Toc159-dependent or independent substrates. We find specific accumulation of the RNP29 precursor in ppi2 but not in wild type or ppil protoplasts. With the exception of Lhcb4, precursor accumulation is also detected with all other tested constructs in ppi2. However, RNP29 is clearly different from the other proteins because only precursor but almost no mature protein is detectable in protoplast extracts. Co-transformation of RN P29 with Toc159 complements its plastid import, supporting the hypothesis that RN P29 is a Toc159-dependent substrate. Exchange of the second amino acid in the RNP29 transit peptide to Glu or Asn prevents methionine excision but not N-terminal acetylation, suggesting that different N-acetyltransferases may act on chloroplast precursor proteins in vivo. All different RNP29 constructs are efficiently imported into wild type but not into ppi2 plastids, arguing for a minor impact of the N-terminal amino acid on the import process.