摘要
根据低分子量谷蛋白亚基(LMW-GS)基因编码区保守序列设计引物,用PCR方法从蛋白质含量低至13.17%的D81和高达27.20%的D42 2份野生二粒小麦(Triticumdicoccoides)中克隆得到2个LMW-GS基因序列LMW-D81和LMW-D42(GenBank上的序列号分别为FJ461691和FJ461690)。它们具有小麦低分子量谷蛋白基因的典型结构特征,其长度分别为1053bp和1011bp,并分别编码350和336个氨基酸残基的成熟蛋白。LMW-D42和LMW-D81的氨基酸序列估算分子量分别为38kDa和39kDa,说明二者均为C型亚基编码基因。LMW-D42和LMW-D81的N-末端序列都为METSHIP-,表明这2个C型亚基编码基因归属LMW-m型。同源性比对和聚类分析揭示,LMW-D81和LMW-D42均属于Glu-B3位点编码基因。LMW-D42和LMW-D81的核苷酸序列和推导的氨基酸序列一致性分别为93.94%和92.57%。与LMW-D81相比,LMW-D42除发生了22处间断性的碱基替换外,还存在一段42个碱基的缺失。对推导氨基酸序列进行的二级结构预测显示,LMW-D81和LMW-D42的蛋白质二级结构高度一致。其α-螺旋主要位于信号肽和C-末端,少量的α-螺旋和不规则卷曲构成了N-末端。大多数不规则卷曲位于重复区,仅有的一段β-折叠则出现在C-末端。同时,它们的编码区均具有分布一致的8个半胱氨酸残基,且第一和第七个半胱氨酸残基均位于无规则卷曲中。这些结构特点对小麦加工品质改良具有一定意义。
In this paper, PCR for the genomic DNA from Triticum dicoccoides was conducted by using a pair of primers designed according to the conservative domain from the known low molecular weight glutenin subunit genes. The two LMW-GS genes, LMW-D81 and LMW-D42 （GenBank accession number FJ461691 and FJ461690）, were obtained from the accession D81 with the low protein content at 13.17% and D42 with the high protein content at 27.20%, respectively. LMW-D42 and LMW-D81 possessed the nucleotide sequences with 1011bp and 1053 bp, and the deduced amino acid sequences with 336 and 350 amino acid residues, respectively. LMW-D42 and LMW-D81 belonged to C type genes owing to their molecular weight about 38 kDa and 39 kDa, respectively, as well as to LMW-m type genes based on the predicted protein sequences of N-terminal domain with METSHIP-. Meanwhile, LMW-D42 and LMW-D81 being allelic Glu-B3 genes were implied by homologous and cluster analyses. The similarities between their sequences were 93.94% in nucleotide and 92.57% in deduced amino acid, respectively. A single deletion for 42 bp occurred in LMW-D42 besides the substitutes at 22 interval sites, compared with LMW-D81. The predicted secondary structures of the amino acid sequences deduced from the two genes were similar. The signal peptide and C-terminal region consisted of many α-helixs. The N-terminal region was formed by a short section of both α-helixs and coils. The repetitive region was mainly occupied by coil. A single β-sheet structure was observed only in C-terminal region. Their amino acid sequences had 8 cysteine residues with similar distri-bution, and the first and seventh cysteine residues located in the coils. So, these structural characters of LMW-D42 and LMW-D81 might be of importance to quality improvement of bread wheat.
出处
《四川农业大学学报》
CSCD
2008年第4期385-392,共8页
Journal of Sichuan Agricultural University
基金
国家自然科学基金(30571139)
四川省教育厅重点项目
四川省学术和技术带头人培养基金
关键词
野生二粒小麦
低分子量谷蛋白
基因克隆
序列分析
二级结构
Triticum dicoccoides
low molecular weight glutenin
gene cloning
sequence analy-sis
secondary structure
