7种植物ALAD基因的生物信息学分析

5-氨基乙酰丙酸脱水酶（8-aminoaevulinicaciddehydratase，ALAD）是生物体所有四吡咯化合物生物合成所必需的酶。目前，GenBank共记载了39种绿色植物的ALAD基因。本文采用生物信息学方法对其中常用的模式植物拟南芥、玉米、小麦、大豆、苜蓿以及葡萄、菠菜等植物的5-氨基乙酰丙酸脱水酶基因的核苷酸及其编码的蛋白氨基酸序列、组成成分、导肽、信号肽、跨膜结构域、疏水性／亲水性、蛋白质二级结构、三级结构及功能域等进行预测和分析，并构建了5-氨基乙酰丙酸脱水酶蛋白家族的系统进化树。结果表明，这几种植物的开放阅读框都在1290bp左右，分子量为47kD左右，等电点（pD值为5．5～7．0之间，ALAD蛋白呈中性至微酸性。含量最丰富的氨基酸为Ala、Leu、Val、Arg、Ser、Gly、Pro和Asp。研究还发现这些植物5-氨基乙酰丙酸脱水酶肽链表现出明显的疏水区和亲水区，不存在信号肽，有叶绿体转运肽；可能存在跨膜结构域。蛋白质二级结构中最主要的结构元件是无规则卷曲和α-螺旋，含有5-氨基乙酰丙酸脱水酶的活性结构域、ALAD-PGBS．aspartate-rich保守结构域、舍夫碱残基结构域和一个镁离子结合位点结构域。核苷酸同源性比对结果显示，拟南芥5-氨基乙酰丙酸脱水酶基因与其它植物的同源性较高；进化分析结果表明这些植物5-氨基乙酰丙酸脱水酶基因被分为六个大类。本工作可为今后深入研究植物5一氨基乙酰丙酸脱水酶的结构特征和功能提供一定的依据。

Bioinformatics Analysis ofALAD Gene in Seven Plants

δ-aminoaevulinic acid dehydratase is necessary to the biosynthesis ofporphyrin compounds in all organ- isms. At present, 39 greenery ALAD genes have been recorded in GenBank. In this paper, the nucleic acid sequences and amino acid sequences ofALAD gene from model plant, such as A rabidopsis thaliana, Zea may, Triticum urartu, Glycine max, Medic ago truncatula, V itis virtife ra, and Sp inac ia ole race a were analyzed by bioinformatics, including the composition of nucleic acid sequences and amino acid sequences, leader peptides, signal peptide, trans-membrane topological structure, hydrohobicity or hydrophilicity, secondary structure, tertiary structure and functional domains of protein and so on. Phylogenetic tree was constructed for the 8-aminoaevulinic acid dehydratase protein family. Results showed that the open reading frame （ORF） of samples is about 1 290, the molecular weight is about 47 kD, the pI is 5.5-7.0 which illustrated that α-aminoaevulinic acid dehydratase is neutral to slightly acidic. The most abundant amino acids residues are Ala, Leu, Val, Arg, Ser, Gly, Pro and Asp. The study also showed that the ALAD protein peptide of these plants showed obvious hydrophobicity area and hydrophilicity area, chloroplast transit peptide; may exists a small amount oftrans-membrane topological structure, no signal peptide. The main secondary structures of the proteins are random coil and Alpha helix. All these proteins have active site, Schiff base residues,