Pérez-Callejón E, Casamayor A, Pujol G, Clua E, Ferrer A, Ariño J
Unitat de Bioquímica, Facultat de Farmàcia, Universitat de Barcelona, Spain.
Plant Mol Biol. 1993 Dec;23(6):1177-85. doi: 10.1007/BF00042351.
In a recent paper [Ariño et al., Plant Mol Biol 21: 475-485 (1993)] we reported the amplification of a DNA fragment (AP-2) from the genome of Arabidopsis thaliana encoding an amino acid sequence corresponding to a Ser/Thr protein phosphatase distantly related to type 2A protein phosphatases. In this paper we report the use of the AP-2 fragment to isolate several cDNA clones from a leaf cDNA library. Two of these (EP124 and EP129) largely overlap and contain the AP-2 sequence, whereas a third clone (EP128) is different although very related in sequence (86% of identity). Clones EP124/EP129 and EP128 were found to encode two highly related polypeptides (93% identity) of 305 residues, showing a very high identity (83%) to the catalytic subunit of protein phosphatase X (PPX) from rabbit. Therefore, they have been named PPX-1 (EP124/EP129) and PPX-2 (EP128). Southern blot analysis of genomic DNA indicates that only these two genes encoding phosphatases closely related to PPX are present in the genome of A. thaliana. Both PPX-1 and PPX-2 are expressed at very low levels in A. thaliana flowers, leaves, stems and roots. The expression levels of four previously identified type 2A phosphatases are higher than those of PPX genes. PP2A-1 appears to be the major mRNA species detected in all the tissues analyzed.
在最近一篇论文中[Ariño等人，《植物分子生物学》21: 475 - 485 (1993)]，我们报道了从拟南芥基因组中扩增出一个DNA片段（AP - 2），该片段编码的氨基酸序列与2A型蛋白磷酸酶有较远亲缘关系的丝氨酸/苏氨酸蛋白磷酸酶相对应。在本文中，我们报道了使用AP - 2片段从叶片cDNA文库中分离出几个cDNA克隆。其中两个（EP124和EP129）有很大重叠且包含AP - 2序列，而第三个克隆（EP128）虽序列上有很大相关性（86%的同一性）但有所不同。发现克隆EP124/EP129和EP128编码两个高度相关的由305个残基组成的多肽（93%的同一性），与兔的蛋白磷酸酶X（PPX）的催化亚基有非常高的同一性（83%）。因此，它们被命名为PPX - 1（EP124/EP129）和PPX - 2（EP128）。基因组DNA的Southern杂交分析表明，拟南芥基因组中仅存在这两个编码与PPX密切相关的磷酸酶的基因。PPX - 1和PPX - 2在拟南芥的花、叶、茎和根中的表达水平都非常低。四个先前鉴定的2A型磷酸酶的表达水平高于PPX基因。PP2A - 1似乎是在所有分析组织中检测到的主要mRNA种类。
