Isolation and Structural Analysis of DNA-binding proteins that are specific to chloroplast DNA

我们确定了编码PD 1、PD 2和PD 3的三种cDNA的核苷酸序列。1.PD1（348个氨基酸残基）含有2个AT-钩，但与其它AT-钩蛋白不同源。在PD 1中还发现了一个跨膜区。免疫印迹分析在叶绿体中检测到50 kDa和87 kDa的条带，以及在细胞核中检测到40 kDa的条带。Southern杂交分析表明，PD 1是由一个多基因家族编码的。PD 2是一个bZIP蛋白，含有6个37个氨基酸的正向重复序列。它在C-末端含有一个跨膜结构域。免疫印迹分析表明，PD 2定位于囊膜。PD 3（1629个残基）含有5个AT钩基序和8个CxxC基序。免疫印迹分析表明，PD 3定位于包膜和类核。发现PD 3在叶绿体内被切割以产生两种多肽。

We determined the nucleotide sequence of three cDNAs that encode PD1, PD2, and PD3. These proteins bind specifically to chloroplast DNA.1.PD1 (348 residues) contained 2 AT-hooks, but it was not homologous to other AT-hook proteins. A membrane-spanning region was also found in PD1. Immunoblot analysis detected bands at 50 kDa and 87 kDa in the chloroplast, as well as a 40 kDa band in the nucleus. Southern blot analysis indicated that PD1 is encoded by a multi gene family.2.PD2 (632 residues) was a bZIP protein, which contained 6 direct repeats of a sequence with 37 residues. It contained a membrane-spanning domain at its C-terminus. Immunoblot analysis suggested that PD2 was localized in the envelope membrane.3.PD3 (1629 residues) contained 5 AT-hook motifs and 8 CxxC motifs. Immunoblot analysis suggested that PD3 was localized in both envelope and nucleoid. PD3 was found to be cleaved within the chloroplast to yield two polypeptides.