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

对编码60kDa蛋白质二硫键异构酶（PDI）的cDNA克隆进行了全长分析。60kDa PDI由511个氨基酸残基组成，其具有KDEL序列作为管腔抗性信号。60 kDa PDI的基因组分析表明，它包含10个外显子和9个内含子间隔。另外还克隆了一个分子量为40kDa的PDI，它由441个氨基酸残基组成，并具有NDEL序列作为腔内驻留信号。两个PDI的同源性约为40%，但都有两个硫氧还蛋白结合位点，这两个位点都存在于PDI酶中。水稻突变体esp2不含60kDa的PDI，对Esp基因的遗传分析表明Esp基因编码60kDa的PDI。对野生型和突变型水稻中60kDa和40kDa的PDI酶活性进行了测定，结果表明，野生型水稻中60kDa和40kDa的PDI酶活性分别占总PDI酶活性的60%和40%，而突变型水稻中没有发现60kDa的PDI酶活性，这意味着100%的PDI酶活性仅来自40kDa的PDI。两种PDI的免疫定位结果表明，60kDa的PDI主要存在于胚乳中，而40kDa的PDI则存在于胚乳和糊粉层中。

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.