The role of protein disulfide isomerase for sorting glutelin and prolamin polypeptides in rice.

对编码60 kDa蛋白质二硫键异构酶(PDI)的全长cDNA克隆进行了分析。60 kDa的PDI由511个氨基酸残基组成，含有KDEL序列，是一个重要的抗性信号。对60 kDa PDI的基因组分析表明，该基因由10个外显子和9个内含子组成。我们还克隆了40 kDa的新型PDI，它由441个氨基酸残基组成，具有作为主要驻留信号的ndel序列。两个PDI之间的同源性约为40%，但它们都有两个存在于PDI酶中的硫氧还蛋白结合位点。水稻突变体ESP2没有60 kDa的PDI，对等位基因ESP基因的遗传分析表明，ESP基因编码60 kDa的PDI。对野生稻和ESP2突变体的60 kDa和40 kDa PDI酶活性的测定表明，野生稻60 kDa和40 kDa的PDI活性分别有60%和40%来自于60 kDa和40 kDa的PDI，而60 kDa的PDI活性在ESP2突变体中没有，这意味着100%的PDI活性仅来自40 kDa的PDI。两种PDI的免疫定位结果表明，60 kDa的PDI主要存在于顶生精子中，而40 kDa的PDI主要存在于胚乳和糊粉层。

Analysis of the full length of cDNA clone encoding 60kDa protein disulfide isomerase (PDI) was done. The 60kDa PDI consists of 511 amino acid residues and it has KDEL sequence as a luminal resitent signal. The genomic analysis of 60 kDa PDI shows that it comprises 10 exons with 9 introns intervals. The novel PDI with 40kDa was also cloned and it consists of 441 amino acid residues and has NDEL sequence as a luminal resident signal. The homology between the two PDIs shows about 40%, but both of them have two thioredoxin binding sites which are present in PDI enzyme. The rice mutant esp2 has no 60kDa PDI and the genetical analysis of Esp genes from allelic lines demonstrates that the Esp gene encodes 60kDa PDI. The enzymatic activities of 60kDa and 40kDa PDIs in a wild and esp2 mutant rices weredetermined ans showed that 60% and 40% of total PDI activities in wild rice comes from 60kDa and 40kD PDIs, respectively, while the 60kDa PDI activity is not seen in the esp2 mutant, meaning that 100% of PDI activity derive from 40kDa PDI alone. The immunolocalization of both PDIs shows that the 60kDa PDI is mainly present in the endpsperm, while the 40kDa PDI both in endosperm and aleurone layer.