玉米21kD富硫种子贮存蛋白的cDNA克隆及其序列分析

cDNA Cloning of the 21 kD Sulfur Rich Seed Storage Protein in Maize and its Sequence Analysis

利用逆转录－聚合酶链式反应（ＲＴ－ＰＣＲ）方法从玉米掖单－２０开花后１０ｄ的叶片中分离到２１ｋＤ玉米种子贮存蛋白ｃＤＮＡ（Ｎ２１ＫＺＹ），并进行了序列分析．其编码蛋白包含２１１个氨基酸，极其富含甲硫氨酸，高达２７％；其Ｎ端有一个２１个氨基酸的信号肽．Ｎ２１ＫＺＹ及其编码蛋白和Ｃｈｕｉ等人分离的该基因的基因组克隆及其编码蛋白的同源性分别为９５．１％和９０．５％；两者的编码蛋白与玉米１０ｋＤ醇溶蛋白极其相似，其中间多出一个５４氨基酸的肽段和一个６氨基酸的肽段，这表明它们可能是来源于同一个祖先基因，后来通过基因重排、缺失或不均等交换等过程而形成的不同的蛋白质．

A total RNA of maize Yedan 20 was extracted from the leaves 10 days after flowering,and a cDNA was obtained from reverse transcript solution of total RNA and a pair of Oligo dT primer.Then,a 21 kD cDNA was isolated from RT PCR products by using a pair of the specific primers.Having recovered from an agarose gel,the specific 21 kD cDNA (N21KZY) was treated and cloned into a pBluescript (KS +) vector.Through screening the blue white colonies,the 21 kD gene was sequenced and characterized.The sequencing result of the 21 kD gene showsed the N21KZY encoded a protein of 211 amino acids,exceptionally rich in methionine up to 27% proportion,with a signal peptide of 21 amino acids in its N terminus.DNA sequence of N21KZY and its encoding protein shared 95 1%,90 5% homology with those of N21KC isolated by Chui et al.Both of their encoding proteins were identical to 10 kD zein,with an extra domain of 54 amino acids and a peptide of 6 amino acids probably caused by gene rearrangement,deletion,non equational interchange or other events of their common ancestor gene.