嗜热蓝藻(Synechococcus elongatus BP-1)别藻蓝蛋白耐热机制的初步研究

来源 :“全球变化下的海洋与湖沼生态安全”学术交流会 | 被引量 : 0次 | 上传用户:leon2000
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  别藻蓝蛋白是藻胆蛋白中的一种,除了作为光合作用捕光天线吸收和高效传递光能外,它也是细胞内的贮存蛋白.别藻蓝蛋白具有优良的荧光特性,在免疫组化、荧光免疫分析等领域已实现了应用.在大肠杆菌中,通过构建嗜热蓝藻别藻蓝蛋白的生物合成途径,我们实现了别藻蓝蛋白α亚基和β亚基的组合生物合成.本文比较了别藻蓝蛋白的热稳定性,利用定点突变技术,初步探讨了别藻蓝蛋白β亚基(holo-apcB)热稳定性的分子基础,主要实验结果如下:1、在大肠杆菌体内分别实现了嗜热藻Synechococcus elongatus BP-1和集胞藻Synechocystis sp.PCC6803(对照)别藻蓝蛋白α亚基(holo-apcA)和β亚基(holo-apcB)的组合生物合成,利用亲和层析对重组蛋白进行了分离纯化,研究热处理对别藻蓝蛋白的荧光强度的影响.研究结果显示:在55℃条件下,Synechococcus elongatus BP-1别藻蓝蛋白α亚基和β亚基半衰期分别为18.9 h和31.9 h,而Synechocystis sp.PCC6803相应值分别为3.3和1.3 h. 嗜热藻Synechococcus elongatus BP-1别藻蓝蛋白的热稳定性明显高于Synechocystis sp.PCC6803. 2、对嗜热藻Synechococcus elongatus BP-1和集胞藻Synechocystis sp.PCC6803别藻蓝蛋白β亚基氨基酸序列进行了比对,二者之间存在十三个差异位点.以Synechococcus elongatus BP-1别藻蓝蛋白β亚基基因为模板,对十三个差异位点分别进行定点突变,突变后该位点与聚胞藻Synechocystis sp.PCC6803别藻蓝蛋白β的对应位点相一致.成功构建出十一个单一位点突变体和三个双位点突变体.所有突变体的半衰期均低于野生型,表明这些位点均与别藻蓝蛋白β亚基的热稳定性相关.半衰期下降最为显著的单突变体为M133I、A125S、A124S,其半衰期分别为2.8 h、4.4 h、9.6h,较野生型分别降低了91.2%、86.2%和69.9%. 双位点突变体A124S/A125S和A29S/I151V半衰期均低于其相应的两个单突变体,而双突变体E25D/N50T半衰期则高于其相应的两个单突变体,表明这些位点之间存在互作,对热稳定性的贡献不是简单的累加作用.
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