极大螺旋藻(Spirulina maxima)藻蓝蛋白基因的克隆及其同源性分析

Cloning and Sequencing of the Phycocyanin Gene from Spirulina maxima and Its Homology Analysis

藻蓝蛋白是红藻和蓝绿藻中一种重要的捕光色素蛋白.克隆了编码极大螺旋藻藻蓝蛋白α和β两个亚基的基因,序列分析表明该基因全长为1119bp.β亚基基因位于α亚基基因上游,两个亚基基因序列长度分别为519bp和489bp,中间被111bp的基因片段间隔.除编码α和β两个亚基的开放阅读密码框外,还存在两个潜在的开放阅读密码框,但这两个密码框的意义还不清楚.比较了该藻蓝蛋白氨基酸序列和来自于其他藻类的藻蓝蛋白氨基酸序列的同源性以及藻蓝蛋白α和β两个亚基之间氨基酸序列的同源性,总的来说其同源性在45.9%～99%之间,α和β两个亚基氨基酸序列同源性为27.1%.藻蓝蛋白包含许多疏水性氨基酸,这些疏水性氨基酸在藻胆蛋白的聚集过程中起着极为重要的作用.分析表明编码藻蓝蛋白α和β两个亚基基因的密码子显示出非对称性.

Phycocyanin is a lightharvesting protein common to bluegreen and red algae. The genes for the two apoprotein subunits, α and β, of phycocyanin from the Spirulina maxima were cloned.They contain 1119 bp. The βsubunit gene is upstream from the αsubunit gene and they are linked together by a 111 bp segment. The βsubunit genecoding region contains 519 bp and the αsubunit genecoding region contains 489 bp. Two potential open reading frames except for these which encode α and βsubunit are also found, but the significance of them is not yet known. The deduced amino acid sequences were compared for homology with the other known phycocyanin sequences. Overall homologies between αsubunit and the other known αsubunit sequences and between βsubunit and the other known βsubunit sequences are between 45.9% and 99% .The homology between αand βsubunit of phycocyanin from the Spirulina maxima is 27.1%. It also contains a significant number of hydrophobic amino acid residues and they play a major role in the aggregation of phycobiliproteins. Codon usage for both the phycocyanin α and βsubunit genes shows asymmetries. 