Weiss M, Pick U
Department of Biochemistry, Weizmann Institute of Science, Rehovot, Israel.
Plant Physiol. 1996 Dec;112(4):1693-702. doi: 10.1104/pp.112.4.1693.
The plasma membrane H(+)-ATPase gene was cloned and sequenced from the extremely acidophilic green alga Dunaliella acidophila and from the extremely halotolerant Dunaliella salina. A special feature of the Dunaliella H(+)-ATPase is an extended C-terminal domain. The deduced amino acid sequences of the two proteins are 75% identical but differ in their C terminus. A hydrophilic loop within this domain in D. salina, which presumably faces the cell exterior, has a high ratio of acidic over basic amino acids, typical of halophilic proteins. The amount of the ATPase protein in plasma membranes and the level of its mRNA transcript in D. acidophila are far higher than in D. salina, suggesting that D. acidophila overexpresses the enzyme. A pH shift from 9.0 to 7.0 induces in D. salina a large increase in the level of the H(+)-ATPase mRNA and in the amount of the H(+)-ATPase protein. This suggests that the expression of the H(+)-ATPase in D. salina is pH-regulated at the transcriptional level. The implications of these findings are discussed with respect to the adaptive pressures imposed on these algal species by their exceptional environmental conditions.
从极端嗜酸绿藻嗜酸杜氏藻（Dunaliella acidophila）和极端耐盐杜氏藻（Dunaliella salina）中克隆并测序了质膜H(+) - ATP酶基因。杜氏藻H(+) - ATP酶的一个特殊特征是其C末端结构域的延伸。这两种蛋白质推导的氨基酸序列有75%相同，但C末端不同。盐生杜氏藻（D. salina）该结构域内的一个亲水环可能面向细胞外部，其酸性氨基酸与碱性氨基酸的比例很高，这是嗜盐蛋白的典型特征。嗜酸杜氏藻质膜中ATP酶蛋白的含量及其mRNA转录本水平远高于盐生杜氏藻，这表明嗜酸杜氏藻过量表达该酶。pH从9.0转变为7.0会导致盐生杜氏藻中H(+) - ATP酶mRNA水平和H(+) - ATP酶蛋白量大幅增加。这表明盐生杜氏藻中H(+) - ATP酶的表达在转录水平受到pH调节。针对这些藻类物种因其特殊环境条件所面临的适应性压力，讨论了这些发现的意义。
