以在细胞中被缓冲。 五、实验证明题。(简要说明,不需详细步骤。每小题5分任选2题, 共10分) 1. Some integral membrane enzymes depend upon the lipids in their microenvironment not only for scaffold ing, but for enzymatic activity. The Nat-K+ ATPase is one example. Please design an experiment to test the influence of membrane fluid ity on the velocity of the Nat- K+ ATPase wers 1. Identify a tissue that would serve as a good source of the enzyme of interest, e.g., the plasma membranes of nerve tissue. Solubilize the Nat-K+ ATPase from its native membrane using detergents. Reconstitute the enzyme into liposomes of simple and well-defined composition, then assay the enzyme fo activity. By synthesizing a variety of liposomes with different amounts of saturated and unsaturated fatty acids, the fluidity of the liposome can be altered and the enzyme can be tested under cond itions of d ifferent fiuid ity from the fatty acid composition, either FRAPor SPT techniques can be erit To measure the fiuid ity of the liposomes directly, without having to infer it applied.) 2.如何证明RNA聚合酶Ⅲ进行5 S rrNA基因转录时,使用的是内部启动 千? 可通过基因操作。如将5 S rRNA基因的5′侧的上游序列完全除去 检测转录情况,然后再切去5 S rrNA基因的部分内部序列,再检测转录情 况。实验结果表明:将5 S rRNA基因的5′侧的上游序列完全除去并不影 响5 S rRNA基因的转录。但是,如果将5 S rrNA基因内部缺失一部分序列 (从50位到80位缺失),RNA聚合酶Ⅲ不仅不能转录这段DNA,甚至不能 结合上去(图6E-1)。如果将5 S rrNA基因的内部启动子序列插入到基因 组的其它部位,会使插入的部位形成一个新的转录起点10 以在细胞中被缓冲。 五、实验证明题。(简要说明，不需详细步骤。每小题 5 分,任选 2 题， 共 10 分)。 1. Some integral membrane enzymes depend upon the lipids in their microenvironment not only for scaffolding, but for enzymatic activity. The Na+-K+ ATPase is one example. Please design an experiment to test the influence of membrane fluidity on the velocity of the Na+-K+ ATPase. Answers: 1. Identify a tissue that would serve as a good source of the enzyme of interest, e.g., the plasma membranes of nerve tissue. Solubilize the Na+-K+ ATPase from its native membrane using detergents. Reconstitute the enzyme into liposomes of simple and well-defined composition, then assay the enzyme for activity. By synthesizing a variety of liposomes with different amounts of saturated and unsaturated fatty acids, the fiuidity of the liposome can be altered, and the enzyme can be tested under conditions of different fiuidity. (To measure the fiuidity of the liposomes directly, without having to infer it from the fatty acid composition, either FRAP or SPT techniques can be applied.) 2. 如何证明 RNA 聚合酶Ⅲ进行 5S rRNA 基因转录时, 使用的是内部启动 子? 可通过基因操作。如将 5S rRNA 基因的 5＇侧的上游序列完全除去， 检测转录情况, 然后再切去 5S rRNA 基因的部分内部序列,再检测转录情 况。实验结果表明: 将 5S rRNA 基因的 5＇侧的上游序列完全除去并不影 响 5S rRNA 基因的转录。但是，如果将 5S rRNA 基因内部缺失一部分序列 (从 50 位到 80 位缺失)，RNA 聚合酶Ⅲ不仅不能转录这段 DNA，甚至不能 结合上去(图 6E-1)。如果将 5S rRNA 基因的内部启动子序列插入到基因 组的其它部位，会使插入的部位形成一个新的转录起点