Cheng S H, Cline K, DeLisle A J
Biochemistry Department, University of Nevada, Reno 89557-0014.
Plant Physiol. 1994 Sep;106(1):303-11. doi: 10.1104/pp.106.1.303.
An Arabidopsis cDNA (Atrbp33) encoding a nuclear-encoded chloroplast RNA-binding protein (RBP) has been isolated (A.J. DeLisle [1993] Plant Physiol 102: 313-314). ATRBP33 shares global structural homology with all known chloroplast RBPs: a chloroplast transit peptide in the amino terminus, followed by a unique acidic domain and a tandem pair of ribonucleoprotein consensus sequence-type RNA-binding domains in the carboxyl end. In vitro translation products of Atrbp33 were found to be imported into chloroplasts, suggesting that ATRBP33 is localized in chloroplasts. The expression of Atrbp33 was higher in chloroplast-containing organs than in nonchloroplast-containing organs. Furthermore, Atrbp33 was expressed in a light-dependent manner. These features are consistent with its postulated role in posttranscriptional control of chloroplast genes. Northern analyses and RNase protection assays showed that as many as nine messages are encoded by the single Atrbp33 gene. Sequence analysis of the cDNAs indicated that some of the transcripts have truncated 5' ends. Most interestingly, the multiple mRNAs potentially encode different polypeptides, one of which lacks a chloroplast transit peptide and acidic domain and contains only one intact RNA-binding domain. Unlike the chloroplast-localized ATRBP33, the truncated polypeptide may function in other cellular compartments.
已分离出一个编码核编码叶绿体RNA结合蛋白（RBP）的拟南芥cDNA（Atrbp33）（A.J. DeLisle [1993]《植物生理学》102: 313 - 314）。ATRBP33与所有已知的叶绿体RBP具有整体结构同源性：氨基末端有一个叶绿体转运肽，接着是一个独特的酸性结构域，羧基末端有一对串联的核糖核蛋白共有序列型RNA结合结构域。发现Atrbp33的体外翻译产物可导入叶绿体，这表明ATRBP33定位于叶绿体中。Atrbp33在含有叶绿体的器官中的表达高于不含叶绿体的器官。此外，Atrbp33以光依赖的方式表达。这些特征与其在叶绿体基因转录后调控中的假定作用一致。Northern分析和RNA酶保护试验表明，单个Atrbp33基因可编码多达9种信息。cDNA的序列分析表明，一些转录本的5'末端被截断。最有趣的是，多个mRNA可能编码不同的多肽，其中一个缺乏叶绿体转运肽和酸性结构域，仅包含一个完整的RNA结合结构域。与定位于叶绿体的ATRBP33不同，截短的多肽可能在其他细胞区室中发挥作用。
